Method for strengthening mainstream anaerobic ammonia oxidation process by using iron-modified diatomite

Abstract

The invention relates to a method for strengthening a mainstream anaerobic ammonia oxidation process by using iron modified diatomite, which adopts an immersed anaerobic ammonia oxidation granular sludge membrane biological composite reactor and comprises the following steps: uniformly mixing an iron element and diatomite in water according to a mass ratio of the iron element to the diatomite of 1: 15-1: 40, drying, and calcining at 450-600 DEG C, iron modified diatomite is obtained; mixing the iron modified diatomite and the inoculated sludge, and adding the mixture into an immersed anaerobic ammonia oxidation granular sludge membrane biological composite reactor, wherein 2.5-3.5 g of the iron modified diatomite and 65-70 mL of the inoculated sludge are added into each 1 L of effective reactor volume; when the concentrations of inlet water ammonia nitrogen and nitrite nitrogen are both 30 + / -2mg / L, executing a mainstream anaerobic ammonia oxidation process; the hydraulic retention time is gradually shortened to improve the nitrogen load, nitrogen is removed, and the anaerobic ammonia oxidation granular sludge is cultured and domesticated. According to the method, iron modified diatomite is taken as a carrier, sludge granulation is enhanced, and rapid starting and efficient and stable operation of a mainstream Anammox process are realized.

Description

Technical Field

[0001] The invention relates to the technical field of mainstream anaerobic ammonium oxidation wastewater denitrification, and in particular to a method for strengthening a mainstream anaerobic ammonium oxidation process by using iron-modified diatomaceous earth. Background Art

[0002] Nitrogen pollution is one of the important environmental problems currently faced. When excessive nitrogen enters the water body, it will cause algae to overgrow, form algal blooms, make the water turbid, and destroy the ecological balance in the water. This not only affects fishery production, but may also produce toxins, posing a threat to aquatic organisms and human health. Compared with the traditional nitrification / denitrification denitrification process, anaerobic ammonium oxidation (Anammox), as an autotrophic biological denitrification process, does not require aeration and external organic carbon sources, and has good environmental friendliness. Since its discovery, it has attracted the attention of researchers all over the world. However, anaerobic ammonium oxidizing bacteria (AnAOB) have the characteristics of low growth rate, high environmental sensitivity, and easy loss, resulting in long start-up cycle and unstable operation of the Anammox process. Especially in the mainstream sewage treatment process, environmental conditions such as lack of substrate and low temperature that are not conducive to the growth of AnAOB make the application of the mainstream Anammox process face greater challenges. Granulated sludge has a dense microbial community, good sedimentation performance, and a stable internal ecosystem, which can effectively increase the biomass and activity of AnAOB in the Anammox reactor. Achieving anaerobic ammonium oxidation sludge granulation is the key to improving the performance of the mainstream Anammox process. However, when the nitrogen load is too high, the granules are prone to disintegration, which can cause the reactor to operate unbalanced. Therefore, it is urgent to find an innovative strategy to enhance the anaerobic ammonium oxidation sludge granulation, improve its stability and activity, and thus improve the performance of the mainstream Anammox process. Summary of the invention

[0003] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for strengthening the mainstream anaerobic ammonium oxidation process by using iron-modified diatomaceous earth. The method uses iron-modified diatomaceous earth as a carrier to strengthen sludge granulation, improve the robust performance and electron transfer of granular sludge, and at the same time improve the enrichment and activity of AnAOB, thereby achieving rapid startup and efficient and stable operation of the mainstream Anammox process.

[0004] The purpose of the present invention is achieved through the following technical solutions: A method for strengthening a mainstream anaerobic ammonium oxidation process by using iron-modified diatomite, the method uses a submerged anaerobic ammonium oxidation granular sludge membrane bioreactor, the composite reactor comprises an upflow anaerobic sludge bed UASB, an MBR is submerged on the upper part of the upflow anaerobic sludge bed UASB; the height-to-diameter ratio of the UASB is 4-6, the MBR is placed on 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: 1. Preparation of iron-modified diatomaceous earth: The iron element and diatomaceous earth are uniformly mixed in water according to the mass ratio of the iron element to the diatomaceous earth of 1:15-1:40, dried, and then calcined at 450-600° C. to obtain iron-modified diatomaceous earth; 2. Mainstream anaerobic ammonium oxidation start-up: The iron-modified diatomaceous earth and the inoculated sludge were mixed and added to the submerged anaerobic ammonium oxidation granular sludge membrane bioreactor. 2.5-3.5g of iron-modified diatomaceous earth and 65-70mL of inoculated sludge were added to each 1L effective reactor volume; 1 / 5-1 / 3 of Anammox sludge was added to the inoculated sludge; the concentrations of ammonia nitrogen and nitrite nitrogen in the influent were both 30±2mg / L, and the mainstream anaerobic ammonium oxidation process was performed. The hydraulic retention time was set to 20 hours, and the effluent NH4 + -N and NO2 - -N is removed simultaneously, and when the average total nitrogen removal rate NRE exceeds 70%, the mainstream Anammox process is successfully started up quickly at a lower ammonia nitrogen concentration; 3. Stable operation: Increase nitrogen load by gradually shortening hydraulic retention time, remove nitrogen, and cultivate and domesticate anaerobic ammonia oxidation granular sludge.

[0005] Furthermore, the submerged anaerobic ammonium oxidation granular sludge membrane biocomposite reactor coupling device comprises a water inlet system, a submerged anaerobic ammonium oxidation granular sludge membrane biocomposite reactor, a water bath circulation system, a water seal structure and a water outlet system; The water inlet system includes a water inlet box 1, a water inlet pipe 2 and a water inlet pump 3, and the water outlet system includes a water outlet 16, a water outlet pipe 17, a water outlet pump 18 and a water outlet box 19; The composite reactor comprises an upflow anaerobic sludge blanket UASB 4, and an MBR 5 is immersed in the upper part of the upflow anaerobic sludge blanket UASB; the height-to-diameter ratio of the UASB is 4-6, the MBR is placed on 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 achieve sludge granulation, and the MBR is used to achieve complete retention of microorganisms, wherein the MBR is an O-type hollow fiber membrane module and is immersed in the UASB; UASB includes an inner tube and an outer tube, and a water bath circulation system 6 is provided between the inner tube and the outer tube; the water bath circulation system is composed of a water bath inlet 7, a water bath outlet 8, a water bath water inlet pipe 9, a water bath water inlet pump 10, a water bath pool 11 and a temperature controller 12; the column space of the inner tube is the main reaction zone, and a gas exhaust port 13 is provided at the upper part of the main reaction zone, and the gas exhaust port is connected by an exhaust pipe 14, and the exhaust pipe is connected to a water seal structure 15; a water outlet 16 of an O-type membrane assembly is provided at the upper part of the main reaction zone, and the water outlet 16 is connected to a water outlet pipe 17, and water is sucked by a water outlet pump 18, and the sucked water is sent to a water outlet tank 19, and a pressure gauge 20 is connected in front of the water outlet pump to record the membrane pollution situation.

[0006] Furthermore, in the stable operation stage of the mainstream Anammox process, the proportion of anaerobic ammonium oxidation particles with a particle size of 1-1.5 mm in the system increases by more than 8% compared with the proportion of anaerobic ammonium oxidation particles formed without adding a carrier under the same conditions, and is preferably 9%-10.0%.

[0007] Furthermore, during the stable operation, by gradually shortening the hydraulic retention time, the total nitrogen removal efficiency was stabilized at more than 80% for four consecutive days at each hydraulic retention time. When the current hydraulic retention time was stable, the next hydraulic retention time was changed to gradually improve the denitrification performance. When the hydraulic retention time was 3h and the entire operation cycle was 91 days, the nitrogen removal efficiency and rate reached 85.91% and 0.437 kg N / (m 3 ·d).

[0008] Furthermore, the mainstream Anammox startup period is less than 20 days, preferably 17 days.

[0009] The preparation process of the iron-modified diatomaceous earth comprises the following steps: 1) Mix diatomaceous earth and ferrous sulfate heptahydrate in a mass ratio of iron element to diatomaceous earth of 1:15-1:40, and add an appropriate amount of deionized water (30-50 mL) to obtain a mixed solution.

[0010] 2) Place the beaker containing the mixture prepared in step 1) on a magnetic stirring mixer and mix at 700 rpm for 2 hours.

[0011] 3) The mixture prepared in 2) was placed in an oven at 80°C and dried for 24 hours.

[0012] 4) The dried sample prepared in step 3) was placed in a muffle furnace and calcined at 500°C for 3 hours.

[0013] 5) Finally, after the sample is cooled, it is washed with anhydrous ethanol and deionized water and dried naturally at room temperature. The final product is iron-modified diatomaceous earth.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention introduces iron-modified diatomaceous earth into the system. On the one hand, the iron element provided by the iron-modified diatomaceous earth is an essential component of iron-containing proteins. Iron-binding proteases such as hydrazine synthase, hydrazine dehydrogenase and nitrite reductase play a vital role in the metabolism and growth of AnAOB. ​​At the same time, the presence of iron accelerates the electron transfer between AnAOB and the substrate, thereby improving 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 granular sludge, making it capable of resisting hydraulic load shock, which is conducive to maintaining high biomass, and also avoids the disintegration and loss of granular sludge caused by high-intensity shear force under low HRT operating conditions, thereby making the system more stable and ensuring the stable operation of the mainstream Anammox process.

[0015] The reactor of the present invention realizes the granulation of sludge and the complete interception of functional bacteria, and then iron-modified diatomaceous earth is added into the reactor as a functional carrier to further enhance the performance of the anaerobic ammonia oxidation granular sludge. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the structure of a submerged anaerobic ammonium oxidation granular sludge membrane biocomposite reactor provided in an embodiment of the present invention; Figure 2 This is a comparison of the macroscopic morphology and SEM microscopic morphology of diatomite and iron-modified diatomite.

[0017] Figure 3 This is a comparison chart of the anaerobic ammonium oxidation activity of diatomaceous earth modified with iron in different mass ratios.

[0018] Figure 4 The figure shows the comparison of nitrogen removal performance in the mainstream Anammox process under the action of iron-modified diatomaceous earth.

[0019] Figure 5 This is a comparison chart between the anaerobic ammonium oxidation granular sludge formed with iron-modified diatomaceous earth as a carrier and the anaerobic ammonium oxidation granular sludge formed without adding a carrier.

[0020] Figure 1 Middle: 1 water inlet tank; 2 water inlet pipe; 3 water 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; 12 temperature controller; 13 exhaust port; 14 exhaust pipe; 15 water seal structure; 16 water outlet; 17 water outlet pipe; 18 water outlet pump; 19 water outlet tank; 20 pressure gauge. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described below in conjunction with specific embodiments and drawings, but this is not intended to limit the protection scope of the present application.

[0022] The following examples use Figure 1 The submerged anaerobic ammonium oxidation granular sludge membrane biocomposite reactor coupling device shown includes an inlet system, a submerged anaerobic ammonium oxidation granular sludge membrane biocomposite reactor, a water bath circulation system, a water seal structure and an outlet system; The water inlet system includes a water inlet box 1, a water inlet pipe 2 and a water inlet pump 3, and the water outlet system includes a water outlet 16, a water outlet pipe 17, a water outlet pump 18 and a water outlet box 19; The composite reactor comprises an upflow anaerobic sludge blanket UASB 4, and an MBR 5 is immersed in the upper part of the upflow anaerobic sludge blanket UASB; the height-to-diameter ratio of the UASB is 4-6, the MBR is placed on 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 achieve sludge granulation, and the MBR is used to achieve complete retention of microorganisms, wherein the MBR is an O-type hollow fiber membrane module and is immersed in the UASB.

[0023] UASB includes an inner tube and an outer tube, and a water bath circulation system 6 is provided between the inner tube and the outer tube. The water bath circulation system consists of a water bath inlet 7, a water bath outlet 8, a water bath water inlet pipe 9, a water bath water inlet pump 10, a water bath pool 11 and a temperature controller 12. The column 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, and the gas exhaust port is connected by an exhaust pipe 14, and the exhaust pipe is connected to a water seal structure 15; a water outlet 16 of an O-type membrane assembly is provided at the top of the main reaction zone, and the water outlet 16 is connected to a water outlet pipe 17, and water is sucked by a water outlet pump 18, and the sucked water is sent to a water outlet tank 19, and a pressure gauge 20 is connected in front of the water outlet pump to record the membrane contamination.

[0024] The lower part of the UASB is a funnel-shaped sludge hopper, and a water inlet is provided at the bottom of the sludge hopper. The water inlet is connected to the water inlet tank through a water inlet pump and a water inlet pipe.

[0025] In the method of the present invention, inoculated sludge containing a small amount of functional bacteria is used, which can synergize with modified diatomaceous earth to significantly accelerate the rapid start-up of the mainstream anaerobic ammonia oxidation process. In the present invention, iron is introduced in the form of being loaded on diatomaceous earth, which prevents the iron salt from being directly added to the system and causing iron crusting. In addition, it also avoids the problem that the iron salt is lost with the effluent and needs to be continuously added, resulting in a high economic cost of the rapid start-up process, which is not conducive to the environment.

[0026] Add 3 g of iron-modified diatomaceous earth and 65-70 mL of inoculated sludge to every 1 L of effective reactor volume.

[0027] Example 1 In this example, UASB (45 cm in height, 10 cm in inner diameter, and aspect ratio of 4.5) was coupled to MBR, where O-type hollow fiber membrane modules (pore size of 0.1 μm and surface area of ​​0.02 m 2 ), the membrane assembly is placed on top of the UASB and the entire length is 20 cm, and the inlet diameter of the UASB is 8 mm. A laboratory-scale SGSMBR (working volume 3 L) was constructed. The coupled reactor includes: an inlet system, a reactor body, a water bath circulation system, a water seal structure and an outlet system.

[0028] The inoculum sludge was a mixture of Anammox sludge (50 mL) and aerobic activated sludge (150 mL), where the aerobic activated sludge came from the aeration tank of the sewage treatment plant.

[0029] The method of strengthening the mainstream anaerobic ammonium oxidation process by using iron-modified diatomaceous earth in this embodiment includes: 1. Preparation of iron-modified diatomaceous earth: 1) Mix diatomaceous earth with different mass ratios and iron from ferrous sulfate heptahydrate (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.

[0030] 2) Place the beaker containing the mixture prepared in step 1) on a magnetic stirring mixer and mix at 700 rpm for 2 hours.

[0031] 3) Place the mixture obtained by mixing in 2) above in an oven at 80°C and dry for 24 hours.

[0032] 4) The dried sample prepared in step 3) was placed in a muffle furnace and calcined at 500°C for 3 hours to load iron in a mixed valence state.

[0033] 5) Finally, after the sample is cooled, it is washed with anhydrous ethanol and deionized water and dried naturally at room temperature. The final product is iron-modified diatomaceous earth.

[0034] The iron-modified diatomaceous earth and the unmodified diatomaceous earth were photographed and tested by SEM. Figure 2The macroscopic morphology and SEM microscopic morphology of diatomite and iron-modified diatomite (1:20) in Example 1 are compared. Diatomite is a pure white powder, while iron-modified diatomite is a brick red powder. The SEM image shows that the surface of diatomite is disc-shaped, the surface is relatively smooth and covered with a large number of ordered multi-level micropores. The surface of iron-modified diatomite is also disc-shaped, but the difference is that its surface is disc-shaped and relatively rough. A large number of irregular small particles can be clearly observed around the micropores. These small particles may be nano-iron oxide particles formed during the pyrolysis process, indicating that iron is successfully loaded on the surface of diatomite.

[0035] Figure 3 The activity comparison chart of anaerobic ammonium oxidation under different iron element and diatomite mass ratios, NH4 + -N and NO2 - -N concentration is 30 mg / L, the reaction time is 10 hours, and the nitrogen concentration of the water sample in the device is tested every two hours. As can be seen from the figure, when there is too much iron, its activity is reduced. When the mass ratio of iron to diatomite is 1:20~1:40, the activity of anaerobic ammonia oxidation can be improved, especially when the mass ratio of iron to diatomite is 1:20, its anaerobic ammonia oxidation activity reaches 54.19 mg N / (g VSS·d), which is the highest activity. When starting up later, iron-modified diatomite with a mass ratio of 1:20 is selected.

[0036] 2. Mainstream anaerobic ammonium oxidation start-up: Iron-modified diatomaceous earth (mass ratio of 1:20) was mixed with inoculum sludge and added into the submerged anaerobic ammonium oxidation granular sludge membrane bioreactor. The concentrations of influent ammonia nitrogen and nitrite nitrogen were both 30 ± 2 mg / L. The mainstream anaerobic ammonium oxidation process was carried out, and the nitrogen load was increased by gradually shortening the hydraulic retention time, and nitrogen removal and cultivation and acclimatization of the anaerobic ammonium oxidation granular sludge were carried out.

[0037] 3 g of iron-modified diatomaceous earth and 65-70 mL of inoculated sludge were added to every 1 L of effective reactor volume. In this embodiment, the total amount of inoculated mixed sludge was 200 mL.

[0038] A continuous water inlet mode was adopted, and the experimental wastewater was simulated wastewater (for the specific configuration process, see Dapena-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 inlet water was stripped with 95% N2 / 5% CO2 for 5 minutes to remove dissolved oxygen.

[0039] The temperature of the reactor was controlled at 20 ± 1 °C. The nitrogen matrix of the influent was ammonia nitrogen (NH4 + -N) and nitrite nitrogen (NO2 - -N) provides, in which the startup phase NH4 + -N and NO2 - -N concentration was set to 30±2 mg / L, hydraulic retention time was set to 20 hours, and effluent NH4 + -N and NO2 - -N is removed synchronously, and when the average total nitrogen removal rate NRE exceeds 70%, the mainstream Anammox process is quickly and successfully started at a lower ammonia nitrogen concentration, and anaerobic ammonium oxidation granular sludge is initially domesticated. In this embodiment, the mainstream Anammox startup cycle is 17 days.

[0040] 3. Stable operation: By gradually shortening the hydraulic retention time, the total nitrogen removal efficiency was stabilized at more than 80% for four consecutive days at each hydraulic retention time. When the current hydraulic retention time was stable, the next hydraulic retention time was replaced to gradually improve the denitrification performance. The hydraulic retention time in the experiment was controlled at 16 h, 12 h, 10 h, 8 h, 6 h, 4 h and 3 h, respectively. When the hydraulic retention time was 3 h and the entire operation cycle was 91 days, the experimental nitrogen removal efficiency and rate reached 85.91% and 0.437 kg N / (m 3·d), indicating that the method of this embodiment has good denitrification performance and good stability. The proportion of anaerobic ammonium oxidation particles with a particle size of 1-1.5 mm in the system increased by 9.82% compared with the proportion of anaerobic ammonium oxidation particles formed without adding a carrier under the same conditions, forming sludge particles with iron-modified diatomaceous earth as the core. The reactor granulates the sludge, and the sludge particles are more dense. During the startup of the mainstream Anammox process, the granular sludge will not disintegrate due to the high flow rate caused by the gradual shortening of the hydraulic retention time.

[0041] Compared with AnGSb (control group without iron-modified diatomaceous earth), the proportion of particles from 1.0 mm to 1.5 mm in the AnGSd system with iron-modified diatomaceous earth added in this example increased by 9.82%, and these relatively large particles had higher bacterial activity, stability and impact resistance, which showed that the addition of Fe-DE had great advantages in optimizing sludge granulation under this system.

[0042] Comparative Example 1 The process of this comparative example is the same as that of Example 1, except that the iron-modified diatomaceous earth in Example 1 is not added to run the mainstream Anammox process. Figure 4 As shown in the figure, the mainstream Anammox startup period in Comparative Example 1 was 29 days (mixed sludge was used as inoculum sludge, but no iron-modified diatomaceous earth was added). After 91 days of stable operation, the nitrogen removal efficiency and rate reached 81.05% and 0.234 kg N / (m 3 ·d).

[0043] The startup period (17 days) in Example 1 is significantly shorter than that in Comparative Example 2, and the nitrogen removal rate is nearly twice that in Comparative Example 1. It can be seen that the method of the present invention is not only conducive to shortening the startup period of the mainstream Anammox process, but also can significantly improve the nitrogen removal performance.

[0044] The electron microscope images of the anaerobic ammonium oxidation granular sludge cultured in Example 1 and the anaerobic ammonium oxidation granular sludge cultured in Comparative Example 1 are as follows: Figure 5 As shown. The anaerobic ammonium oxidation granular sludge in Comparative Example 1 mainly consists of cocci and brevis, accompanied by a small amount of filamentous bacteria, and the cocci show a cauliflower structure unique to AnAOB. ​​In the anaerobic ammonium oxidation granular sludge cultured in Example 1, the vast majority are cocci, which significantly reduces the number of brevis, and the cauliflower structure is more compact, indicating that its AnAOB enrichment is higher.

[0045] And the content of S and Fe elements in the anaerobic ammonium oxidation granular sludge cultured in Example 1 (4.62% and 20.61%) is about twice that in Comparative Example 1 (2.82% and 12.88%). The increase in the intracellular Fe and S content is conducive to promoting the synthesis of Fe-S protein, which is an important redox center component in the electron transfer process and promotes the electron transfer of granular sludge. In addition, the integrity coefficient of the granular sludge in Comparative Example 1 is 89.13%, which is significantly lower than 96.47% in Example 1, which shows that the granular sludge in Example 1 has better shear resistance, which is conducive to improving the stability of the granular sludge and alleviating the loss of bacteria. The granular sludge formed with iron-modified diatomaceous earth as a carrier enhances its structural strength and stability, so that it can effectively resist the impact of hydraulic load, which is not only conducive to maintaining high biomass, but also avoids the disintegration and loss of granular sludge due to high-intensity shear force under low hydraulic retention time operation conditions, thereby further improving the stability of the system and ensuring the stable operation of the Anammox process. Thereby achieving stable and efficient denitrification performance.

[0046] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A method for strengthening the mainstream anaerobic ammonium oxidation process using iron-modified diatomaceous earth, characterized in that: The method uses an immersed anaerobic ammonium oxidation granular sludge membrane bioreactor, the composite reactor includes an upflow anaerobic sludge bed UASB, and an MBR is immersed on the upper part of the upflow anaerobic sludge bed UASB; the height-to-diameter ratio of the UASB is 4-6, the MBR is placed on 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:

1. Preparation of iron-modified diatomaceous earth: The iron element and diatomaceous earth are uniformly mixed in water according to the mass ratio of the iron element to the diatomaceous earth of 1:15-1:40, dried, and then calcined at 450-600° C. to obtain iron-modified diatomaceous earth; 2. Mainstream anaerobic ammonium oxidation start-up: The iron-modified diatomaceous earth and the inoculated sludge were mixed and added to the submerged anaerobic ammonium oxidation granular sludge membrane bioreactor. 2.5-3.5g of iron-modified diatomaceous earth and 65-70mL of inoculated sludge were added to each 1L effective reactor volume; 1 / 5-1 / 3 of Anammox sludge was added to the inoculated sludge; the concentrations of ammonia nitrogen and nitrite nitrogen in the influent were both 30±2mg / L, and the mainstream anaerobic ammonium oxidation process was performed. The hydraulic retention time was set to 20 hours, and the effluent NH4 + -N and NO2 - -N is removed simultaneously, and when the average total nitrogen removal rate NRE exceeds 70%, the mainstream Anammox process is successfully started up quickly at a lower ammonia nitrogen concentration; 3. Stable operation: Increase nitrogen load by gradually shortening hydraulic retention time, remove nitrogen, and cultivate and domesticate anaerobic ammonia oxidation granular sludge.

2. The method according to claim 1, characterized in that The iron element provided by the iron-modified diatomaceous earth is an essential component of iron-containing proteins. At the same time, the presence of iron accelerates the electron transfer between AnAOB and the substrate, thereby improving the enrichment and activity of AnAOB. ​​At the same time, using iron-modified diatomaceous earth as a carrier, the granular sludge is enriched with the iron-modified diatomaceous earth as the core, which enhances the structural strength and stability of the granular sludge and enables it to resist the impact of hydraulic loads. While maintaining a high biomass, it avoids the disintegration and loss of granular sludge caused by high-intensity shear forces under low HRT operating conditions, thereby making the system more stable and ensuring the stable operation of the mainstream Anammox process.

3. The method according to claim 1, characterized in that The submerged anaerobic ammonium oxidation granular sludge membrane biocomposite reactor coupling device comprises a water inlet system, a submerged anaerobic ammonium oxidation granular sludge membrane biocomposite reactor, a water bath circulation system, a water seal structure and a water outlet system; The water inlet system includes a water inlet box, 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 box; The composite reactor comprises an upflow anaerobic sludge blanket UASB, and an MBR is immersed in the upper part of the upflow anaerobic sludge blanket UASB; the height-to-diameter ratio of the UASB is 4-6, the MBR is placed on 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 achieve sludge granulation, and the MBR is used to achieve complete retention of microorganisms, wherein the MBR is an O-type hollow fiber membrane module and is immersed in the UASB; UASB includes an inner tube and an outer tube, and a water bath circulation system is between the inner tube and the outer tube; the water bath circulation system consists of a water bath inlet, a water bath outlet, a water bath water inlet pipe, a water bath water inlet pump, a water bath pool and a temperature controller; the column space of the inner tube is the main reaction zone, and a gas exhaust port is provided at the top of the main reaction zone, and the gas exhaust port is connected by an exhaust pipe, and the exhaust pipe is connected to a water seal structure; a water outlet of an O-type membrane assembly is provided at the top of the main reaction zone, and the water outlet is connected to a water outlet pipe, and water is sucked by a water outlet pump, and the sucked water is sent to a water outlet tank, and a pressure gauge is connected in front of the water outlet pump to record the membrane contamination.

4. The method according to claim 1, characterized in that During the stable operation stage of the mainstream Anammox process, the proportion of anaerobic ammonium oxidation particles with a particle size of 1-1.5 mm in the system increases by more than 8% compared with the proportion of anaerobic ammonium oxidation particles formed without adding a carrier under the same conditions, and is preferably 9%-10.0%.

5. The method according to claim 1, characterized in that During the stable operation, by gradually shortening the hydraulic retention time, the total nitrogen removal efficiency was stabilized at more than 80% for four consecutive days at each hydraulic retention time. When the current hydraulic retention time was stable, the next hydraulic retention time was replaced to gradually improve the denitrification performance. When the hydraulic retention time was 3h and the entire operation cycle was 91 days, the nitrogen removal efficiency and rate reached 85.91% and 0.437 kg N / (m 3 ·d).

6. The method according to claim 1, characterized in that The mainstream Anammox startup cycle is less than 20 days, preferably 17 days.

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