Methods for enhancing mainstream anaerobic ammonium oxidation processes with iron-modified diatomaceous earth

Abstract

This invention relates to a method for enhancing mainstream anaerobic ammonia oxidation (ANAO) using iron-modified diatomaceous earth. The method utilizes a submerged anaerobic ammonia oxidation granular sludge membrane bioreactor. The process involves: uniformly mixing iron and diatomaceous earth in water at a mass ratio of 1:15-1:40, drying the mixture, and then calcining it at 450-600℃ to obtain iron-modified diatomaceous earth; mixing the iron-modified diatomaceous earth with inoculum sludge and adding it to the submerged ANAO granular sludge membrane bioreactor, with 2.5-3.5 g of iron-modified diatomaceous earth and 65-70 mL of inoculum sludge added per 1 L of effective reactor volume; maintaining an influent ammonia nitrogen and nitrite nitrogen concentration of 30 ± 2 mg / L, and executing the mainstream ANAO process; gradually increasing the nitrogen loading by gradually shortening the hydraulic retention time to remove nitrogen and cultivate and acclimatize the anaerobic ammonia oxidation granular sludge. This method enhances sludge granulation by using iron-modified diatomaceous earth as a carrier, enabling rapid start-up and efficient and stable operation of the mainstream Anammox process.

Description

Technical Field

[0001] This invention relates to the field of mainstream anaerobic ammonia oxidation wastewater denitrification technology, and more specifically to a method for enhancing mainstream anaerobic ammonia oxidation processes with iron-modified diatomaceous earth. Background Technology

[0002] Nitrogen pollution is a significant environmental problem. Excessive nitrogen entering water bodies leads to algal blooms, causing turbidity and disrupting the aquatic ecosystem. This not only impacts fisheries but can also produce toxins, threatening aquatic life and human health. Compared to traditional nitrification / denitrification processes, anammox, as an autotrophic biological nitrogen removal process, requires no aeration or external organic carbon source and boasts excellent environmental friendliness, attracting global attention since its discovery. However, anammox bacteria (AnAOBs) are characterized by low growth rates, high environmental sensitivity, and easy loss, resulting in long start-up periods and operational instability in the Anammox process. Particularly in mainstream wastewater treatment processes, unfavorable environmental conditions such as substrate scarcity and low temperatures further challenge the application of mainstream Anammox processes. Granular sludge, with its dense microbial community, good settling properties, and stable internal ecosystem, can effectively improve the biomass and activity of AnAOBs in Anammox reactors. Achieving granulation of anammox sludge is crucial for improving the performance of mainstream Anammox processes. However, when nitrogen loading is too high, the granules are prone to disintegration, leading to reactor imbalance. Therefore, there is an urgent need to find an innovative strategy to enhance the granulation of anammox sludge, improve its stability and activity, and thus improve the performance of mainstream Anammox processes. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a method for enhancing mainstream anaerobic ammonia oxidation processes using iron-modified diatomaceous earth. This method enhances sludge granulation by using iron-modified diatomaceous earth as a carrier, thereby improving the robustness and electron transport of granular sludge, and simultaneously increasing the enrichment and activity of AnAOB, thus enabling rapid start-up and efficient and stable operation of the mainstream Anammox process.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A method for enhancing mainstream anaerobic ammonium oxidation (ANAO) processes with iron-modified diatomaceous earth is disclosed. The method utilizes a submerged anaerobic ammonium oxidation granular sludge membrane bioreactor (MBR). The MBR comprises an upflow anaerobic sludge blanket (UASB) with a microbiota reactor (MBR) submerged above the UASB. The UASB has a height-to-diameter ratio of 4-6, and the MBR is positioned at the top of the UASB with an overall length of 1 / 2-1 / 3 of the UASB height. The process is as follows:

[0006] I. Preparation of iron-modified diatomaceous earth:

[0007] Iron-modified diatomaceous earth is obtained by mixing iron and diatomaceous earth evenly in water at a mass ratio of 1:15 to 1:40, drying the mixture, and then calcining it at 450-600℃.

[0008] II. Start-up of mainstream anaerobic ammonium oxidation:

[0009] Iron-modified diatomaceous earth was mixed with inoculated sludge and added to a submerged anaerobic ammonia oxidation granular sludge membrane bioreactor. 2.5-3.5 g of iron-modified diatomaceous earth and 65-70 mL of inoculated sludge were added per 1 L of effective reactor volume. The inoculated sludge contained 1 / 5-1 / 3 Anammox sludge. The influent ammonia nitrogen and nitrite nitrogen concentrations were both 30 ± 2 mg / L. A mainstream anaerobic ammonia oxidation process was implemented, with a hydraulic retention time of 20 hours. The effluent NH4+... + -N and NO2 - -N was removed simultaneously, and when the average total nitrogen removal rate (NRE) exceeded 70%, the mainstream Anammox process was able to start up quickly and successfully at a low ammonia nitrogen concentration.

[0010] III. Stable Operation: By gradually shortening the hydraulic retention time to increase the nitrogen load, nitrogen removal is carried out, and the anaerobic ammonia oxidation granular sludge is cultivated and acclimatized.

[0011] Furthermore, the submerged anammox granular sludge membrane bioreactor coupling device includes an influent system, a submerged anammox granular sludge membrane bioreactor, a water bath circulation system, a water seal structure, and an effluent system.

[0012] The water inlet system includes a water inlet tank 1, a water inlet pipe 2, and a water inlet pump 3; the water outlet system includes a water outlet 16, a water outlet pipe 17, a water outlet pump 18, and a water outlet tank 19.

[0013] The composite reactor includes an upflow anaerobic sludge blanket (UASB) 4, with an MBR 5 submerged above the UASB; the height-to-diameter ratio of the UASB is 4-6, the MBR is positioned at the top of the UASB, and the overall length of the MBR is 1 / 2-1 / 3 of the height of the UASB.

[0014] The UASB is used to achieve sludge granulation, and the MBR is used to achieve complete retention of microorganisms. The MBR is an O-type hollow fiber membrane module immersed in the UASB.

[0015] The UASB consists of an inner tube and an outer tube, with a water bath circulation system 6 between them. The water bath circulation system comprises a water bath inlet 7, a water bath outlet 8, a water bath inlet pipe 9, a water bath inlet pump 10, a water bath tank 11, and a temperature controller 12. The cylindrical space of the inner tube is the main reaction zone, and a gas exhaust port 13 is provided at the top of the main reaction zone. The gas exhaust port is connected by an exhaust pipe 14, which is connected to a water seal structure 15. An outlet 16 of the O-type membrane module is provided at the top of the main reaction zone. The outlet 16 is connected to an outlet pipe 17, and water is drawn by an outlet pump 18. The drawn water is sent to an outlet tank 19. A pressure gauge 20 is connected before the outlet pump to record the membrane fouling status.

[0016] Furthermore, during the stable operation phase of the mainstream Anammox process, the proportion of anaerobic ammonia oxidation particles with a diameter of 1-1.5 mm in the system increases by more than 8% compared to the proportion of anaerobic ammonia oxidation particles formed under the same conditions without the addition of a carrier, preferably 9%-10.0%.

[0017] Furthermore, during stable operation, by gradually shortening the hydraulic retention time, the total nitrogen removal efficiency remained stable above 80% for four consecutive days at each hydraulic retention time. Once stable operation at the current hydraulic retention time was achieved, the next hydraulic retention time was introduced, gradually improving the nitrogen removal performance. When the hydraulic retention time was 3 hours and the entire operation cycle was 91 days, the nitrogen removal efficiency and rate reached 85.91% and 0.437 kg N / (m³), respectively. 3 ·d).

[0018] Furthermore, the startup cycle of mainstream Anammox is less than 20 days, preferably 17 days.

[0019] The preparation process of the iron-modified diatomite includes the following steps:

[0020] 1) Mix diatomaceous earth with ferrous sulfate heptahydrate at a mass ratio of iron to diatomaceous earth of 1:15-1:40, and add an appropriate amount of deionized water (30-50mL) to obtain a mixture.

[0021] 2) Place the beaker containing the mixture from 1) above on a magnetic stirrer and mix at 700 rpm for 2 hours.

[0022] 3) Place the mixture from 2) above in an oven at 80°C and dry for 24 hours.

[0023] 4) Place the dried sample from step 3) into a muffle furnace and calcine it at 500°C for 3 hours.

[0024] 5) Finally, after the sample has cooled, it is washed with anhydrous ethanol and deionized water and then dried naturally at room temperature. The final product is iron-modified diatomaceous earth.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] This invention introduces iron-modified diatomaceous earth into the system. On one hand, the iron provided by the iron-modified diatomaceous earth serves as an essential component of iron-containing proteins. Iron-binding proteases such as hydrazine synthase, hydrazine dehydrogenase, and nitrite reductase play crucial roles in the metabolism and growth of AnAOB. ​​Simultaneously, the presence of iron accelerates electron transfer between AnAOB and the substrate, thereby enhancing the enrichment and activity of AnAOB. ​​On the other hand, using iron-modified diatomaceous earth as a carrier enhances the structural strength and stability of the granular sludge, enabling it to resist hydraulic load shocks. This helps maintain high biomass and simultaneously avoids the disintegration and loss of granular sludge that may occur under low HRT operating conditions due to high-intensity shear forces, thus making the system more stable and ensuring the stable operation of the mainstream Anammox process.

[0027] The reactor of this invention achieves sludge granulation and complete retention of functional bacteria. Then, iron-modified diatomaceous earth is added to the reactor as a functional carrier to further enhance the performance of anaerobic ammonia oxidation granular sludge. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the submerged anammox granular sludge membrane bioreactor provided in an embodiment of the present invention.

[0029] Figure 2 Comparison of macroscopic morphology and SEM microscopic morphology of diatomite and iron-modified diatomite.

[0030] Figure 3 A comparison of anaerobic ammonium oxidation activity under different mass ratios of iron-modified diatomaceous earth.

[0031] Figure 4 This is a comparison chart of nitrogen removal performance in the mainstream Anammox process under the action of iron-modified diatomaceous earth.

[0032] Figure 5 This is a comparison diagram of anaerobic ammonia oxidation granular sludge formed with iron-modified diatomaceous earth as a carrier and anaerobic ammonia oxidation granular sludge formed without a carrier.

[0033] Figure 1Components: 1. Inlet tank; 2. Inlet pipe; 3. Inlet pump; 4. UASB; 5. MBR; 6. Water bath circulation system; 7. Water bath inlet; 8. Water bath outlet; 9. Water bath inlet pipe; 10. Water bath inlet pump; 11. Water bath tank; 12. Temperature controller; 13. Vent; 14. Vent pipe; 15. Water seal structure; 16. Outlet; 17. Outlet pipe; 18. Outlet pump; 19. Outlet tank; 20. Pressure gauge. Detailed Implementation

[0034] The technical solution of the present invention will be further described below with reference to specific embodiments and accompanying drawings, but this is not intended to limit the scope of protection of this application.

[0035] The following examples use, for example Figure 1 The submerged anammox granular sludge membrane bioreactor coupling device shown includes an influent system, a submerged anammox granular sludge membrane bioreactor, a water bath circulation system, a water seal structure, and an effluent system.

[0036] The water inlet system includes a water inlet tank 1, a water inlet pipe 2, and a water inlet pump 3; the water outlet system includes a water outlet 16, a water outlet pipe 17, a water outlet pump 18, and a water outlet tank 19.

[0037] The composite reactor includes an upflow anaerobic sludge blanket (UASB) 4, with an MBR 5 submerged above the UASB; the height-to-diameter ratio of the UASB is 4-6, the MBR is positioned at the top of the UASB, and the overall length of the MBR is 1 / 2-1 / 3 of the height of the UASB.

[0038] The UASB is used to achieve sludge granulation, and the MBR is used to achieve complete microbial retention. The MBR is an O-type hollow fiber membrane module immersed in the UASB.

[0039] The UASB consists of an inner tube and an outer tube, connected by a water bath circulation system 6. The water bath circulation system comprises a water bath inlet 7, a water bath outlet 8, a water bath inlet pipe 9, a water bath inlet pump 10, a water bath tank 11, and a temperature controller 12. The cylindrical space of the inner tube is the main reaction zone. A gas exhaust port 13 is located at the top of the main reaction zone, connected to an exhaust pipe 14, which in turn connects to a water seal structure 15. An O-type membrane module outlet 16 is located at the top of the main reaction zone, connected to an outlet pipe 17. An outlet pump 18 draws water from the outlet, which is then sent to an outlet tank 19. A pressure gauge 20 is connected before the outlet pump to record membrane fouling status.

[0040] The lower part of the UASB is a funnel-shaped sludge hopper, and the bottom of the sludge hopper is provided with a water inlet. The water inlet is connected to the water tank through a water pump and a water pipe.

[0041] In this invention, inoculated sludge containing a small amount of functional bacteria is used, which can synergistically work with modified diatomaceous earth to significantly accelerate the rapid start-up of mainstream anaerobic ammonia oxidation processes. In this invention, iron is introduced in the form of a load on the diatomaceous earth, preventing the formation of iron crusts due to the direct addition of iron salts to the system. Furthermore, this avoids the problem of iron salts being lost with the effluent and requiring continuous addition, which would result in high economic costs for the rapid start-up process and be detrimental to the environment.

[0042] Add 3g of iron-modified diatomaceous earth and 65-70mL of inoculum sludge to each 1L of effective reactor volume.

[0043] Example 1

[0044] In this embodiment, a UASB (45 cm high, 10 cm inner diameter, height-to-diameter ratio 4.5) is coupled to an MBR, wherein the MBR uses an O-type hollow fiber membrane module (pore size 0.1 μm, surface area 0.02 m²). 2 The membrane module is positioned at the top of the UASB and has a total length of 20 cm. The inlet diameter of the UASB is 8 mm. A laboratory-scale SGSMBR (working volume 3 L) was constructed. The coupled reactor includes: an influent system, a reactor body, a water bath circulation system, a water seal structure, and an effluent system.

[0045] The inoculated sludge was a mixture of Anammox sludge (50 mL) and aerobic activated sludge (150 mL), wherein the aerobic activated sludge came from the aeration tank of the wastewater treatment plant.

[0046] The method for enhancing mainstream anaerobic ammonia oxidation process with iron-modified diatomaceous earth in this embodiment includes:

[0047] I. Preparation of iron-modified diatomaceous earth:

[0048] 1) Mix diatomaceous earth with iron from ferrous sulfate heptahydrate in different mass ratios (the mass ratio of iron to diatomaceous earth is set to 1:1, 1:5, 1:10, 1:20, 1:40), and add 50 mL of deionized water.

[0049] 2) Place the beaker containing the mixture from 1) above on a magnetic stirrer and mix at 700 rpm for 2 hours.

[0050] 3) Place the mixture from 2) above in an oven at 80°C and dry for 24 hours.

[0051] 4) Place the dried sample from step 3) into a muffle furnace and calcine it at 500°C for 3 hours, with iron loaded in a mixed valence state.

[0052] 5) Finally, after the sample has cooled, it is washed with anhydrous ethanol and deionized water and then dried naturally at room temperature. The final product is iron-modified diatomaceous earth.

[0053] The iron-modified diatomaceous earth and the unmodified diatomaceous earth were photographed and subjected to SEM testing. Figure 2 For the comparison of macroscopic morphology and SEM microscopic morphology of diatomaceous earth and iron-modified diatomaceous earth (1:20) in Example 1, diatomaceous earth is a pure white powder, while iron-modified diatomaceous earth appears as a brick-red powder. SEM images show that the surface of diatomaceous earth is disc-shaped, relatively smooth, and covered with a large number of ordered hierarchical micropores. The surface of iron-modified diatomaceous earth is also disc-shaped, but unlike diatomaceous earth, it is more rough. A large number of irregular small particles can be clearly observed distributed around the micropores. These small particles may be nano-iron oxide particles formed during pyrolysis, indicating that iron was successfully loaded onto the surface of the diatomaceous earth.

[0054] Figure 3 A comparison chart of the activity of anaerobic ammonium oxidation under different iron and diatomaceous earth mass ratios, NH4 + -N and NO2 - The concentration of -N was 30 mg / L, and the reaction time was 10 hours. Nitrogen concentration in the water sample was measured every two hours. The graph shows that excessive iron reduces activity. When the mass ratio of iron to diatomaceous earth is 1:20 to 1:40, the activity of anaerobic ammonia oxidation is improved. Especially when the mass ratio of iron to diatomaceous earth is 1:20, the activity of anaerobic ammonia oxidation reaches the highest level of 54.19 mg N / (g VSS·d). Iron-modified diatomaceous earth with a mass ratio of 1:20 was selected for subsequent start-up.

[0055] II. Start-up of mainstream anaerobic ammonium oxidation:

[0056] Iron-modified diatomaceous earth (mass ratio 1:20) was mixed with inoculated sludge and added to a submerged anammox granular sludge membrane bioreactor. The concentrations of ammonia nitrogen and nitrite nitrogen in the influent were both 30 ± 2 mg / L. The mainstream anammox process was executed, and the nitrogen load was increased by gradually shortening the hydraulic retention time to remove nitrogen and cultivate and acclimatize the anammox granular sludge.

[0057] Add 3g of iron-modified diatomaceous earth and 65-70mL of inoculated sludge to each 1L of effective reactor volume. In this example, the total amount of mixed inoculated sludge is 200mL.

[0058] A continuous influent mode was adopted, and the experimental wastewater was simulated wastewater (for specific configuration procedures, please refer to Daphna-Mora, A., Van Hulle, SWH, Luis, Campos J., Mendez, R. Vanrolleghem, PA Jetten, M., 2004. Enrichment of Anammox biomass from municipal activated sludge: experimental and modelling results. J. Chem. Technol. Biotechnol. 79:1421-1428.). The influent was stripped with 95% N2 / 5% CO2 for 5 minutes to remove dissolved oxygen.

[0059] The reactor temperature was controlled at 20±1℃. The influent nitrogen substrate consisted of ammonia nitrogen (NH4). + -N) and nitrite nitrogen (NO2) - -N) is provided, where the startup phase NH4 + -N and NO2 - The -N concentration was set to 30±2 mg / L, the hydraulic retention time was set to 20 hours, and the effluent NH4+ concentration was... + -N and NO2 - -N was removed simultaneously, and when the average total nitrogen removal rate (NRE) exceeded 70%, the mainstream Anammox process was successfully started up rapidly at a low ammonia nitrogen concentration, and anaerobic ammonia oxidation granular sludge was initially acclimated. In this embodiment, the start-up period of the mainstream Anammox process was 17 days.

[0060] III. Stable operation:

[0061] By gradually shortening the hydraulic retention time, the total nitrogen removal efficiency was stabilized above 80% for four consecutive days at each hydraulic retention time. Once stable operation at the current hydraulic retention time was achieved, the next hydraulic retention time was introduced, gradually improving the nitrogen removal performance. The hydraulic retention times in the experiment were controlled at 16 h, 12 h, 10 h, 8 h, 6 h, 4 h, and 3 h. When the hydraulic retention time was 3 h and the entire operating cycle was 91 days, the experimental nitrogen removal efficiency and rate reached 85.91% and 0.437 kg N / (m³), respectively. 3•d) This demonstrates that the method in this embodiment exhibits good denitrification performance and stability. Furthermore, the proportion of anaerobic ammonia oxidation particles with a diameter of 1-1.5 mm in the system increased by 9.82% compared to anaerobic ammonia oxidation particles formed under the same conditions without the addition of a carrier. This resulted in sludge particles with an iron-modified diatomaceous earth core. The reactor granulates the sludge, making the particles more compact. During the startup of the mainstream Anammox process, the increased flow velocity due to the gradually shortening hydraulic retention time will not cause the granular sludge to disintegrate.

[0062] Compared to AnGSb (control group without iron-modified diatomaceous earth), the proportion of 1.0 mm to 1.5 mm particles in the AnGSd system with iron-modified diatomaceous earth in this embodiment increased by 9.82%. These relatively larger particles have higher bacterial activity, stability and shock resistance, which indicates that the addition of Fe-DE has a great advantage in optimizing sludge granulation in this system.

[0063] Comparative Example 1

[0064] The process for this comparative example is the same as that for Example 1, except that the iron-modified diatomaceous earth used in Example 1 is not added, and the mainstream Anammox process is run. A comparison of the denitrification performance of Example 1 and Comparative Example 1 is provided. Figure 4 As shown in the figure, the start-up period of the mainstream Anammox in Comparative Example 1 was 29 days (using mixed sludge as inoculum sludge, but without adding iron-modified diatomaceous earth). After 91 days of stable operation, the nitrogen removal efficiency and rate reached 81.05% and 0.234 kg N / (m³), respectively. 3 ·d).

[0065] The start-up period (17 days) in Example 1 was significantly shorter than that in Comparative Example 2, and the nitrogen removal rate was almost twice that in Comparative Example 1. Therefore, the method of the present invention not only helps to shorten the start-up period of the mainstream Anammox process, but also significantly improves nitrogen removal performance.

[0066] Electron micrographs of the anaerobic ammonia oxidation granular sludge cultured in Example 1 and Comparative Example 1 are shown below. Figure 5 As shown. The anaerobic ammonia oxidation granular sludge in Comparative Example 1 mainly consists of cocci and short bacilli, with a small amount of filamentous bacteria. The cocci exhibit the cauliflower-like structure characteristic of AnAOB. ​​In contrast, the anaerobic ammonia oxidation granular sludge cultured in Example 1 is predominantly composed of cocci, with a significant reduction in the number of short bacilli, and the cauliflower-like structure is more compact, indicating a higher enrichment degree of AnAOB.

[0067] Furthermore, the S and Fe content in the anaerobic ammonia oxidation granular sludge cultured in Example 1 (4.62% and 20.61%) was approximately twice that of Comparative Example 1 (2.82% and 12.88%). The increased intracellular Fe and S content promotes the synthesis of Fe-S proteins, which are important redox center components in electron transport, thus facilitating electron transport in the granular sludge. In addition, the integrity coefficient of the granular sludge in Comparative Example 1 was 89.13%, significantly lower than the 96.47% in Example 1. This indicates that the granular sludge in Example 1 has better shear resistance, which is beneficial for improving the stability of the granular sludge and mitigating strain loss. The granular sludge formed using iron-modified diatomaceous earth as a carrier enhances its structural strength and stability, enabling it to effectively resist the impact of hydraulic loads. This not only helps maintain high biomass but also avoids the granular sludge disintegration and loss that may occur due to high shear forces under low hydraulic retention time operating conditions, thereby further improving system stability and ensuring the stable operation of the Anammox process. This achieves stable and efficient nitrogen removal performance.

[0068] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A method for enhancing the mainstream anaerobic ammonia oxidation process by iron-modified diatomite, characterized in that, The method uses an immersed anaerobic ammonia oxidation granular sludge membrane biological composite reactor, the composite reactor includes an upflow anaerobic sludge bed (UASB) and an MBR immersed in the upper part of the UASB; the height-diameter ratio of the UASB is 4-6, the MBR is arranged at the top of the UASB, and the overall length of the MBR is 1 / 2-1 / 3 of the height of the UASB; the process of the method is as follows: I. Preparation of iron-modified diatomite: Iron elements and diatomite are mixed in water according to a mass ratio of 1:15-1:40, dried, and calcined at 450-600 DEG C to obtain iron-modified diatomite; II. Mainstream anaerobic ammonia oxidation start-up: The iron modified diatomite is mixed with inoculated sludge and added into the submerged anaerobic ammonia oxidation granular sludge membrane biological composite reactor, 2.5-3.5g of iron modified diatomite and 65-70mL of inoculated sludge are added into every 1L of effective reactor volume; 1 / 5-1 / 3 of Anammox sludge is added into the inoculated sludge; the concentration of ammonia nitrogen and nitrite nitrogen in the influent is 30±2mg / L, the main stream anaerobic ammonia oxidation process is executed, the hydraulic retention time is set to 20 hours, the effluent NH4 + -N and NO2 - -N is removed synchronously, when the average total nitrogen removal rate NRE exceeds 70%, the rapid successful start of the main stream Anammox process at a lower ammonia nitrogen concentration is realized; III. Stable operation: nitrogen removal and cultivation and domestication of anaerobic ammonia oxidation granular sludge are performed by gradually shortening the hydraulic retention time to increase the nitrogen load.

2. The method of claim 1, wherein, The iron elements provided by the iron-modified diatomite serve as essential components of iron-containing proteins, and the presence of the iron elements accelerates electron transfer between AnAOB and substrates, thereby improving the enrichment and activity of AnAOB; meanwhile, the iron-modified diatomite is used as a carrier, and the granular sludge is enriched with the iron-modified diatomite as the core, which enhances the structural strength and stability of the granular sludge, enables the granular sludge to resist hydraulic load impact, maintains high biomass, and avoids possible disintegration and loss of the granular sludge due to high-intensity shear force under low-HRT operating conditions, thereby making the system more stable and ensuring stable operation of the mainstream Anammox process.

3. The method of claim 1, wherein, The immersed anaerobic ammonia oxidation granular sludge membrane biological composite reactor coupling device includes a water inlet system, an immersed anaerobic ammonia oxidation granular sludge membrane biological composite reactor, a water bath circulation system, a water seal structure, and a water outlet system. The water inlet system includes a water inlet tank, a water inlet pipe, and a water inlet pump, and the water outlet system includes a water outlet, a water outlet pipe, a water outlet pump, and a water outlet tank. The composite reactor includes an upflow anaerobic sludge bed (UASB) and an MBR immersed in the upper part of the UASB; the height-diameter ratio of the UASB is 4-6, the MBR is arranged at the top of the UASB, and the overall length of the MBR is 1 / 2-1 / 3 of the height of the UASB; The UASB is used to realize granulation of sludge, and the MBR is used to realize complete interception of microorganisms, wherein the MBR is an O-shaped hollow fiber membrane assembly and is immersed in the UASB; The UASB includes an inner layer pipe and an outer layer pipe, and the water bath circulation system is arranged between the inner layer pipe and the outer layer pipe; the water bath circulation system is composed of a water bath inlet, a water bath outlet, a water bath inlet pipe, a water bath inlet pump, a water bath pool, and a temperature controller; the column space of the inner layer pipe is a main reaction zone, a gas exhaust port is arranged at the upper part of the main reaction zone, the gas exhaust port is connected by an exhaust pipe, the exhaust pipe is connected to the water seal structure, a water outlet of the O-shaped membrane assembly is arranged at the upper part of the main reaction zone, the water outlet is connected to a water outlet pipe, and water is pumped out by a water outlet pump, the pumped-out water is sent to a water outlet tank, and a pressure gauge is connected before the water outlet pump to record membrane pollution.

4. The method of claim 1, wherein, In the stable operation stage of the mainstream Anammox process, the proportion of anaerobic ammonia oxidation particles with a particle size of 1-1.5 mm in the system is increased by more than 8% compared with the proportion of anaerobic ammonia oxidation particles formed under the same conditions without adding carriers.

5. The method of claim 4, wherein, In the stable operation stage of the mainstream Anammox process, the proportion of anaerobic ammonia oxidation particles with a particle size of 1-1.5 mm in the system is increased by 9%-10.0% compared with the proportion of anaerobic ammonia oxidation particles formed under the same conditions without adding carriers.

6. The method of claim 1, wherein, In the stable operation process, by gradually shortening the hydraulic retention time, the total nitrogen removal efficiency is continuously stable at more than 80% for four days under each hydraulic retention time, the current hydraulic retention time is stably operated, then the next hydraulic retention time is replaced, the denitrification performance is gradually improved, and when the hydraulic retention time is 3h, the whole operation cycle is 91 days, the nitrogen removal efficiency and rate reach 85.91% and 0.437 kg N / (m 3 d).

7. The method of claim 1, wherein, The startup period of the mainstream Anammox process is less than 20 days.

8. The method of claim 7, wherein, The startup period of the mainstream Anammox process is 17 days.

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