A method for promoting the activity of total nitrifiers

Abstract

The application provides a method for promoting the activity of total nitrification bacteria, and the method promotes the activity of total nitrification bacteria by externally adding hydroxylamine in the process of converting ammonium salt into nitrate in total nitrification, greatly improves the conversion and utilization capacity of ammonium salt, and achieves the purpose of improving ammonia nitrogen removal. The method successfully promotes the activity of total nitrification bacteria, improves the conversion efficiency of ammonia nitrogen, and can quickly improve the ammonia nitrogen removal capacity of total nitrification bacteria in a short period. The method successfully realizes the promotion of the activity of total nitrification bacteria by externally adding hydroxylamine, more efficiently converts ammonium salt in wastewater into nitrate, and improves the conversion rate of ammonia nitrogen and the generation concentration of nitrate.

Description

Technical Field

[0001] This invention relates to a method for promoting the activity of nitrifying bacteria throughout the entire process, belonging to the field of biotechnology. Background Technology

[0002] Since the discovery of nitrifying microorganisms in the late 19th century, it was generally believed that nitrification was accomplished by two types of microorganisms: ammonia nitrogen was oxidized to nitrite by ammonia-oxidizing microorganisms (including ammonia-oxidizing bacteria and ammonia-oxidizing archaea), and then oxidized to nitrate by nitrite-oxidizing bacteria. However, a 2006 study proposed that, based on the kinetic theory of optimal path length, the one-step oxidation of ammonia nitrogen to nitrate theoretically requires less energy and is more likely to occur. Therefore, it was suggested that a nitrifying bacterium might exist in nature that simultaneously possesses genes for both ammonia oxidation and nitrite oxidation. However, it wasn't until 2015 that this microorganism capable of one-step nitrification was discovered and named *Comammox*.

[0003] Studies have shown that all discovered nitrifying bacteria possess the complete genes encoding ammonia monooxygenase (AMO), hydroxylamine dehydrogenase (HAO), and nitrite oxidoreductase (NXR), demonstrating their genetic potential to completely oxidize ammonia to nitrate. The specific steps are as follows: First, ammonia is converted to hydroxylamine (NH₂OH) by ammonia monooxygenase; then, hydroxylamine dehydrogenase converts it to nitrite; and finally, nitrite oxidoreductase oxidizes it to nitrate (NH₄⁺). + →NH2OH→NO2 - →NO3 - In this process, hydroxylamine is an intermediate product. Currently, most reports on comammox focus on its distribution, activity, and laboratory enrichment culture in various natural habitats. There are also some patent documents reporting on comammox, but most concern enrichment culture. For example, Chinese patent document CN111635862A discloses a method for enriching and culturing nitrifying bacteria throughout the entire process; Chinese patent document CN109851064A discloses a sequencing batch reactor (SBR) device and method for enriching nitrifying bacteria throughout the entire process based on soft packing material; and Chinese patent document CN109851065A discloses a sand-like filter-type device and method for enriching nitrifying bacteria throughout the entire process.

[0004] The above information pertains to the enrichment of nitrifying bacteria throughout the entire process. It is generally believed that comammox bacteria have a long enrichment period and low activity. To apply comammox bacteria to ammonia nitrogen removal from wastewater, improving the ammonia nitrogen conversion rate of comammox bacteria is crucial. This type of research is still in its early stages, and there is a lack of research on intermediate products. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for promoting the activity of nitrifying bacteria throughout the entire process.

[0006] This invention, during the nitrification process where ammonium salts are converted to nitrates, enhances the activity of nitrifying bacteria by externally adding hydroxylamine, significantly improving their ability to convert and utilize ammonium salts, thereby increasing ammonia nitrogen removal. The method of this invention successfully promotes the activity of nitrifying bacteria throughout the entire nitrification process, improves ammonia nitrogen conversion efficiency, and can rapidly enhance the ammonia nitrogen removal capacity of nitrifying bacteria in a short period.

[0007] Terminology Explanation:

[0008] Complete nitrifying bacteria (comammox): comammox bacteria use NH4+ as the active ingredient. + As a substrate, it is passed through NH2OH and NO2. - Ultimately oxidized to NO3 - The reaction formula is NH4 + →NH2OH→NO2 - →NO3 - .

[0009] Sequencing batch membrane bioreactor (SBBR): a novel water treatment reactor that combines membrane separation unit and biological treatment unit.

[0010] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0011] A method for promoting the activity of nitrifying bacteria throughout the entire process includes the following steps:

[0012] (1) After pretreatment of activated sludge containing comammox bacteria, it is inoculated into a sequencing batch biofilm reactor (SBBR) and packing is added to ensure that the sludge and packing are in full contact.

[0013] (2) Wastewater is introduced into the reactor and it is operated in a cycle of water inlet-aeration-sedimentation-drainage. During the operation of the reactor, the pH is maintained at 7±0.1 and the temperature is controlled at 35±2℃.

[0014] (3) During operation, no hydroxylamine is added to the reactor during the first 1-5 days of operation. From the 6th to the 19th day of operation, hydroxylamine is added to make the concentration of hydroxylamine in the reactor 3-20 mg / L, which promotes the activity of nitrifying bacteria throughout the process and rapidly improves the ability of nitrifying bacteria to remove ammonia nitrogen in a short period of time.

[0015] According to a preferred embodiment of the present invention, in step (1), the activated sludge containing comammox bacteria is obtained by the following means:

[0016] The flocculent sludge in the aerobic tank of the municipal wastewater treatment plant was pretreated by soaking, washing, and filtration. 1-5 liters of the pretreated flocculent sludge were then inoculated into a sequencing batch biofilm reactor (SBBR), along with polyurethane packing material to ensure sufficient contact between the sludge and the packing. The reactor cycle was 12 hours, with each cycle consisting of 0.5 hours of influent, 10 hours of aeration, 0.5 hours of settling, and 1 hour of effluent discharge before starting the next cycle. The volume exchange ratio for each cycle was 1.5:1. The DO concentration during the aeration phase was controlled at 0.2-0.5 mg / L, and the pH was maintained at 7±0.1. A constant-temperature water bath was used to maintain the reactor temperature at 37℃ to avoid the influence of light on bacterial growth. The reactor operated in a dark environment for 120 days to effectively enrich nitrifying bacteria throughout the process.

[0017] According to a preferred embodiment of the present invention, during the entire nitrifying bacteria enrichment process, the influent is artificially simulated wastewater with the following composition: ammonium chloride (NH4Cl) content 90-100 mg / L, potassium dihydrogen phosphate (KH2PO4) content 40-60 mg / L, potassium chloride (KCl) content 70-80 mg / L, magnesium sulfate (MgSO4·7H2O) content 40-60 mg / L, sodium chloride (NaCl) content 580-600 mg / L, trace element solution content 0.5-5 mL / L, selenium-tungsten solution content 0.5-5 mL / L, and calcium carbonate (CaCO3) content 2-8 g / L;

[0018] The trace element solution contains the following components: manganese sulfate (MnSO4·1H2O) 34.4 mg / L, boric acid (H3BO3) 50 mg / L, zinc chloride (ZnCl2) 34.4 mg / L, sodium molybdate (Na2MoO4) 72.6 mg / L, copper chloride (CuSO4·2H2O) 20 mg / L, nickel chloride (NiCl2·6H2O) 24 mg / L, cobalt chloride (CoCl2·6H2O) 80 mg / L, and ferrous sulfate (FeSO4·7H2O) 1 g / L.

[0019] The selenium-tungsten solution has the following composition: sodium hydroxide (NaOH) content 0.5 g / L, sodium selenite (Na2SeO3·5H2O) content 3 mg / L, and sodium tungstate (Na2WO4·2H2O) content 4 mg / L.

[0020] According to a preferred embodiment of the present invention, in step (1), the sequencing batch membrane bioreactor is made of plexiglass material and has a constant temperature water bath layer on its outer periphery.

[0021] According to a preferred embodiment of the present invention, in step (1), the filler is a polyurethane filler with a density of 0.015-0.03 g / cm³. 3 The surface area is 5000 cm². 2 / g, porosity >95%, pore size 2-2.5mm, square shape.

[0022] According to a preferred embodiment of the present invention, in step (1), the filling volume ratio of the packing material is 45-55%, and the inoculation volume of activated sludge containing comammox bacteria is one-third of the entire reactor.

[0023] The polyurethane packing material used in the entire nitrifying bacteria enrichment process is the same as that used in step (1), and the filling volume ratio is also the same.

[0024] The filler of this invention is a milky white square shape with abundant pores, and features a large specific surface area, short biofilm formation time, wide applicability, and long service life.

[0025] According to a preferred embodiment of the present invention, in step (2), the wastewater contains 90-100 mg / L of ammonium chloride (NH4Cl), 40-60 mg / L of potassium dihydrogen phosphate (KH2PO4), 70-80 mg / L of potassium chloride (KCl), 40-60 mg / L of magnesium sulfate (MgSO4·7H2O), 580-600 mg / L of sodium chloride (NaCl), 0.5-5 mL / L of trace element solution, 0.5-5 mL / L of selenium-tungsten solution, and 2-8 g / L of calcium carbonate (CaCO3).

[0026] According to a preferred embodiment of the present invention, the trace element solution composition is as follows: manganese sulfate (MnSO4·1H2O) content 34.4 mg / L, boric acid (H3BO3) content 50 mg / L, zinc chloride (ZnCl2) content 34.4 mg / L, sodium molybdate (Na2MoO4) content 72.6 mg / L, copper chloride (CuSO4·2H2O) content 20 mg / L, nickel chloride (NiCl2·6H2O) content 24 mg / L, cobalt chloride (CoCl2·6H2O) content 80 mg / L, and ferrous sulfate (FeSO4·7H2O) content 1 g / L.

[0027] According to a preferred embodiment of the present invention, the selenium-tungsten solution has the following composition: sodium hydroxide (NaOH) content 0.5 g / L, sodium selenite (Na2SeO3·5H2O) content 3 mg / L, and sodium tungstate (Na2WO4·2H2O) content 4 mg / L.

[0028] According to a preferred embodiment of the present invention, in step (2), the nitrogen in the wastewater is mainly ammonium salt.

[0029] According to a preferred embodiment of the present invention, in step (2), the sequencing batch reactor is in a cycle of 12 hours. In each cycle, the water is fed for 0.5 hours, aerated for 10 hours, and left to stand for 0.5 hours before being discharged. After 1 hour of discharge, the next cycle begins. The volume exchange ratio in each cycle is 1.5:1, and the DO concentration during the aeration stage of the reactor is controlled to be 0.2-0.5 mg / L.

[0030] According to a preferred embodiment of the present invention, in step (3), the added hydroxylamine is hydroxylamine hydrochloride (NH2OH·HCl).

[0031] According to a preferred embodiment of the present invention, in step (3), hydroxylamine is added to make the concentration of hydroxylamine in the reactor 4-8 mg / L.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] 1. This invention uses the addition of hydroxylamine to promote the activity of nitrifying bacteria throughout the process. The electrons obtained by hydroxylamine in the conversion of nitrite are recycled to AMO enzyme, triggering its activity and increasing ammonium consumption. This successfully converts ammonium salts in wastewater into nitrates more efficiently, improves the ammonia nitrogen conversion rate, and achieves the goal of improving the activity of nitrifying bacteria throughout the process.

[0034] 2. This invention utilizes a sequencing batch membrane bioreactor to immobilize Comamox bacteria, which can maintain high Comamox bacteria activity within the membrane; and due to the efficient separation effect of the membrane, the sludge and effluent are completely separated, ensuring the long-term stable operation of the system.

[0035] 3. The reactor of this invention incorporates packing material to facilitate better attachment and growth of nitrifying bacteria throughout the process. During reactor operation, the influent is ammonium-containing wastewater, the reaction cycle is 12 hours, and the volume exchange ratio for each cycle is 1.5:1. Temperature, pH, and dissolved oxygen (DO) are maintained at a stable level. Attached Figure Description

[0036] Figure 1 This is a diagram showing the nitrogen conversion effect of adding hydroxylamine to promote the activity of nitrifying bacteria throughout the process, as described in this invention. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0038] In this embodiment, a sequencing batch membrane bioreactor (SBR) is used. Water is pumped into the reactor, and the dissolved oxygen (DO) concentration is controlled to be 0.2-0.5 mg / L using gas flow rate. To ensure uniform water distribution and sufficient contact with the sludge, an internal circulation system is implemented to increase turbulence. The effluent is controlled by an effluent pump to maintain a balance between the influent and effluent within the reactor.

[0039] The enriched nitrifying bacteria sludge in the example:

[0040] Flocculent sludge from the aerobic tank of a municipal wastewater treatment plant was pretreated by soaking, washing, and filtration. 1.2 liters of the pretreated flocculent sludge was then inoculated into a sequencing batch biofilm reactor (SBBR), along with polyurethane packing material to ensure sufficient contact between the sludge and the packing. The reactor operated for 12 hours per cycle, with 0.5 hours of influent, 10 hours of aeration, 0.5 hours of settling, and 1 hour of effluent discharge before starting the next cycle. The volume exchange ratio for each cycle was 1.5:1. The dissolved oxygen (DO) concentration during aeration was controlled at 0.2-0.5 mg / L, and the pH was maintained at 7±0.1. A constant-temperature water bath was used to maintain the reactor temperature at 37°C to avoid the influence of light on bacterial growth. The reactor operated in a dark environment for 120 days, effectively enriching nitrifying bacteria throughout the process.

[0041] The influent was artificially simulated wastewater with the following composition: ammonium chloride (NH4Cl) 96 mg / L, potassium dihydrogen phosphate (KH2PO4) 50 mg / L, potassium chloride (KCl) 75 mg / L, magnesium sulfate (MgSO4·7H2O) 50 mg / L, sodium chloride (NaCl) 584 mg / L, calcium carbonate (CaCO3) 4 g / L, trace element solution 1 mL / L, and selenium-tungsten solution 1 mL / L.

[0042] The trace element solution contains the following components: manganese sulfate (MnSO4·1H2O) 34.4 mg / L, boric acid (H3BO3) 50 mg / L, zinc chloride (ZnCl2) 34.4 mg / L, sodium molybdate (Na2MoO4) 72.6 mg / L, copper chloride (CuSO4·2H2O) 20 mg / L, nickel chloride (NiCl2·6H2O) 24 mg / L, cobalt chloride (CoCl2·6H2O) 80 mg / L, and ferrous sulfate (FeSO4·7H2O) 1 g / L.

[0043] The selenium-tungsten solution has the following composition: sodium hydroxide (NaOH) content 0.5 g / L, sodium selenite (Na2SeO3·5H2O) content 3 mg / L, and sodium tungstate (Na2WO4·2H2O) content 4 mg / L.

[0044] Example 1:

[0045] A method for promoting the activity of nitrifying bacteria throughout the entire process, comprising the following steps:

[0046] (1) Select sludge enriched and cultured in the laboratory with full-process nitrifying bacteria, wash the sludge several times with tap water until the washing liquid is transparent, then pour off the washing liquid and inoculate it into the sequencing batch membrane bioreactor. The inoculation volume is one-third of the entire reactor.

[0047] (2) The reactor influent is artificially simulated nitrogen-containing wastewater. The sequencing batch reactor is set to a cycle of 12 hours. In each cycle, the effluent is discharged for 1 hour, the influent is discharged for 0.5 hours, the aeration reaction is carried out for 10 hours, and the effluent is allowed to stand for 0.5 hours before the next cycle is expected. The volume exchange ratio of each cycle is 1.5:1. The DO concentration during the aeration stage of the reactor is controlled by a gas flow meter to be 0.2-0.5 mg / L. The pH is maintained at 7±0.1 during the operation of the reactor. A constant temperature water bath is set up to maintain the reactor temperature at 37℃.

[0048] The simulated nitrogen-containing wastewater contained 96 mg / L ammonium chloride (NH4Cl), 50 mg / L potassium dihydrogen phosphate (KH2PO4), 75 mg / L potassium chloride (KCl), 50 mg / L magnesium sulfate (MgSO4·7H2O), 584 mg / L sodium chloride (NaCl), 4 g / L calcium carbonate (CaCO3), 1 mL / L trace element solution, and 1 mL / L selenium-tungsten solution.

[0049] The trace element solution contains the following components: manganese sulfate (MnSO4·1H2O) 34.4 mg / L, boric acid (H3BO3) 50 mg / L, zinc chloride (ZnCl2) 34.4 mg / L, sodium molybdate (Na2MoO4) 72.6 mg / L, copper chloride (CuSO4·2H2O) 20 mg / L, nickel chloride (NiCl2·6H2O) 24 mg / L, cobalt chloride (CoCl2·6H2O) 80 mg / L, and ferrous sulfate (FeSO4·7H2O) 1 g / L.

[0050] The selenium-tungsten solution has the following composition: sodium hydroxide (NaOH) content 0.5 g / L, sodium selenite (Na2SeO3·5H2O) content 3 mg / L, and sodium tungstate (Na2WO4·2H2O) content 4 mg / L.

[0051] (3) During operation, no hydroxylamine is added to the reactor during the first 1-5 days of operation. On the 6th day of operation, hydroxylamine is added to make the concentration of hydroxylamine in the reactor 4 mg / L, which promotes the activity of nitrifying bacteria throughout the process and rapidly improves the ability of nitrifying bacteria to remove ammonia nitrogen in a short period of time.

[0052] Test results are as follows Figure 1 As shown, before the addition of hydroxylamine, the ammonia nitrogen removal rate was between 85.09% and 89.14%. After the addition of hydroxylamine, the NO3 removal rate in the effluent decreased. - Both the concentration and the ammonia nitrogen removal rate showed an upward trend. Except for the 8th and 9th days when the ammonia nitrogen removal rate was below 90%, the removal rate was generally above 95% for the rest of the time.

[0053] Example 2:

[0054] The method for promoting the activity of nitrifying bacteria throughout the entire process is the same as described in Example 1, except that:

[0055] In step (3), during the operation of the reactor, hydroxylamine was added on the 8th day to make the concentration of hydroxylamine in the reactor 5 mg / L, which promoted the activity of nitrifying bacteria throughout the process and quickly improved the ability of nitrifying bacteria to remove ammonia nitrogen in a short period of time.

[0056] Example 3:

[0057] The method for promoting the activity of nitrifying bacteria throughout the entire process is the same as described in Example 1, except that:

[0058] In step (3), during the operation of the reactor, hydroxylamine was added on the 10th day to make the concentration of hydroxylamine in the reactor 6 mg / L, which promoted the activity of nitrifying bacteria throughout the process and rapidly improved the ability of nitrifying bacteria to remove ammonia nitrogen in a short period of time.

[0059] Example 4:

[0060] The method for promoting the activity of nitrifying bacteria throughout the entire process is the same as described in Example 1, except that:

[0061] In step (3), during the operation of the reactor, hydroxylamine was added on the 12th day to make the concentration of hydroxylamine in the reactor 8 mg / L, which promoted the activity of nitrifying bacteria throughout the process and rapidly improved the ability of nitrifying bacteria to remove ammonia nitrogen in a short period of time.

[0062] Example 5:

[0063] The method for promoting the activity of nitrifying bacteria throughout the entire process is the same as described in Example 1, except that:

[0064] In step (3), during the operation of the reactor, hydroxylamine was added on the 14th day to make the concentration of hydroxylamine in the reactor 10 mg / L, which promoted the activity of nitrifying bacteria throughout the process and rapidly improved the ability of nitrifying bacteria to remove ammonia nitrogen in a short period of time.

[0065] As can be seen from the examples, adding hydroxylamine to the SBBR reactor can promote the activity of nitrifying bacteria throughout the process, and improve the ammonia nitrogen conversion rate and nitrate concentration.

Claims

1. A method for promoting the activity of comammox bacteria, comprising the following steps: (1) Pretreating activated sludge containing comammox bacteria, inoculating into a sequencing batch biofilm reactor (SBBR), adding fillers, and making the sludge fully contact with the fillers; The activated sludge containing comammox bacteria is obtained by the following means: The flocculent sludge in the aerobic tank of a municipal sewage plant is pretreated by soaking, cleaning and filtering, 1-5 liters of pretreated flocculent sludge is inoculated into a sequencing batch biofilm reactor (SBBR), and polyurethane fillers are added to make the sludge fully contact with the fillers, the reactor is 12 hours for one cycle, 0.5 hours for water feeding, 10 hours for aeration reaction, 0.5 hours for standing, 1 hour for water discharge, and the next cycle is carried out, the volume exchange ratio of each cycle is 1.5:1, the DO concentration in the aeration stage of the reactor is controlled to be 0.2-0.5 mg / L, the pH is maintained at 7±0.1, a constant temperature water bath layer is set to maintain the temperature of the reactor at 37℃, and the influence of light on the growth of bacterial flora is avoided, the reactor is operated in a light-proof environment, and the reactor is operated for 120 days to make the comammox bacteria effectively enriched; During the enrichment of comammox bacteria, the influent is artificial simulated wastewater, and the composition is as follows: the content of ammonium chloride (NH4Cl) is 90-100 mg / L, the content of potassium dihydrogen phosphate (KH2PO4) is 40-60 mg / L, the content of potassium chloride (KCl) is 70-80 mg / L, the content of magnesium sulfate (MgSO4·7H2O) is 40-60 mg / L, the content of sodium chloride (NaCl) is 580-600 mg / L, the content of trace element solution is 0.5-5 mL / L, the content of selenium-tungsten solution is 0.5-5 mL / L, and the content of calcium carbonate (CaCO3) is 2-8 g / L; The composition of the trace element solution is as follows: the content of manganese sulfate (MnSO4·1H2O) is 34.4 mg / L, the content of boric acid (H3BO3) is 50 mg / L, the content of zinc chloride (ZnCl2) is 34.4 mg / L, the content of sodium molybdate (Na2MoO4) is 72.6 mg / L, the content of copper chloride is 20 mg / L, the content of nickel chloride (NiCl2·6H2O) is 24 mg / L, the content of cobalt chloride (CoCl2·6H2O) is 80 mg / L, and the content of ferrous sulfate (FeSO4·7H2O) is 1 g / L; The composition of the selenium-tungsten solution is as follows: the content of sodium hydroxide (NaOH) is 0.5 g / L, the content of sodium selenite (Na2SeO3·5H2O) is 3 mg / L, and the content of sodium tungstate (Na2WO4·2H2O) is 4 mg / L; (2) The wastewater is introduced into the reactor, and the reactor is periodically operated in the mode of influent-aeration-stand-by-drainage, the pH is maintained at 7±0.1 during the operation of the reactor, and the temperature is controlled at 35±2℃; (3) During the operation, no hydroxylamine is added in the reactor for the first 5 days, hydroxylamine is added to make the concentration of hydroxylamine in the reactor be 4-8 mg / L for the operation from the 6th day to the 19th day, the activity of comammox bacteria is promoted, and the ability of comammox bacteria to remove ammonia nitrogen is rapidly improved in a short period of time; the added hydroxylamine is hydroxylamine hydrochloride (NH2OH·HCl).

2. The method of claim 1, wherein, In step (1), the sequencing batch reactor (SBR) uses plexiglass material and is surrounded by a constant-temperature water bath. The packing material is polyurethane packing with a density of 0.015-0.03 g / cm³. 3 The surface area is 5000 cm². 2 / g, porosity >95%, pore size 2-2.5mm, square shape.

3. The method of claim 1, wherein, In step (1), the filling volume ratio of the filler is 45-55%, and the volume of the comammox bacteria-containing activated sludge inoculum is one-third of the entire reactor.

4. The method of claim 1, wherein, In step (2), the wastewater contains 90-100 mg / L of ammonium chloride (NH4Cl), 40-60 mg / L of potassium dihydrogen phosphate (KH2PO4), 70-80 mg / L of potassium chloride (KCl), 40-60 mg / L of magnesium sulfate (MgSO4·7H2O), 580-600 mg / L of sodium chloride (NaCl), 0.5-5 mL / L of trace element solution, 0.5-5 mL / L of selenium-tungsten solution, and 2-8 g / L of calcium carbonate (CaCO3).

5. The method of claim 4, wherein, The trace element solution contains 34.4 mg / L of manganese sulfate (MnSO4·1H2O), 50 mg / L of boric acid (H3BO3), 34.4 mg / L of zinc chloride (ZnCl2), 72.6 mg / L of sodium molybdate (Na2MoO4), 20 mg / L of copper chloride, 24 mg / L of nickel chloride (NiCl2·6H2O), 80 mg / L of cobalt chloride (CoCl2·6H2O), and 1 g / L of ferrous sulfate (FeSO4·7H2O); The selenium-tungsten solution contains 0.5 g / L of sodium hydroxide (NaOH), 3 mg / L of sodium selenite (Na2SeO3·5H2O), and 4 mg / L of sodium tungstate (Na2WO4·2H2O).

6. The method of claim 1, wherein, In step (2), the nitrogen in the wastewater is mainly in the form of ammonium salt, and the sequencing batch biofilm reactor has a cycle of 12 hours, with 0.5 hours of water inflow, 10 hours of aeration reaction, 0.5 hours of standing, 1 hour of water outflow, and then the next cycle. The volume exchange ratio of each cycle is 1.5:1, and the DO concentration in the aeration stage of the reactor is controlled at 0.2-0.5 mg / L.

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