A method for deep denitrification of landfill leachate

Abstract

The present application relates to the field of wastewater treatment, and discloses a deep denitrification method for landfill leachate in a waste transfer station, comprising the following steps: passing wastewater into an anaerobic tank to perform denitrification; passing the effluent from the anaerobic tank into an anoxic tank to perform short-cut denitrification and anaerobic ammonia oxidation; passing the effluent from the anoxic tank into an aerobic tank to perform aerobic and anaerobic ammonia oxidation by using aerobic and anaerobic ammonia-oxidizing bacteria respectively loaded on the outer layer and the inner layer of biological fillers; refluxing part of the sludge-water mixture at the end of the aerobic tank into the anoxic tank, and passing the rest into a membrane bioreactor to separate sludge and water, degrade organic matter by using heterotrophic bacteria under aeration, and simultaneously convert ammonia into nitrate; and refluxing part of the sludge-water mixture in the membrane bioreactor into the anaerobic tank. The deep denitrification method can realize good cooperation between multiple denitrification pathways, avoid the defects of a single denitrification pathway, has less dependence on carbon sources, has less aeration amount and sludge yield, and has lower requirements for denitrification conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wastewater treatment, and particularly relates to a deep denitrification method for landfill leachate in a waste transfer station. BACKGROUND

[0002] Landfill leachate containing a large amount of nitrogen will be produced in the process of a waste transfer station. If the landfill leachate is directly discharged into the environment, the nitrogen will cause eutrophication and other problems, which will threaten human health and environmental safety. Therefore, the nitrogen in the leachate needs to be deeply removed.

[0003] There are physical and chemical methods and biochemical methods for wastewater denitrification. The physical and chemical methods include stripping / stripping technology, ion exchange technology, membrane separation technology, chemical precipitation technology, advanced oxidation technology, etc. These technologies have problems such as increased treatment cost caused by additional reagents and high energy consumption, and secondary pollution. In comparison, the biochemical method has great advantages.

[0004] General biological denitrification is that ammonia-oxidizing bacteria and nitrite-oxidizing bacteria oxidize ammonia to nitrite under sufficient dissolved oxygen, and then nitrite is oxidized to nitrate. Subsequently, denitrifying bacteria reduce nitrate to nitrogen gas under anoxic conditions using organic matter as a carbon source, and the nitrogen gas is released into the atmosphere, thereby achieving wastewater denitrification. The above denitrification process requires a large amount of aeration and additional organic carbon source. However, due to the limited biodegradable organic matter in the landfill leachate of the waste transfer station, there is often a shortage of carbon source, so additional organic carbon source is needed to supplement, which increases the treatment cost. Compared with general denitrification technology, anaerobic ammonia oxidation technology has great advantages. Anaerobic ammonia oxidation denitrification is a process in which anaerobic ammonia-oxidizing bacteria oxidize ammonia to nitrogen gas under anoxic conditions using nitrite as an electron acceptor. As can be seen, anaerobic ammonia oxidation does not require additional organic carbon source, and ammonia only needs to be oxidized to nitrite, which saves aeration amount. Studies have shown that the sludge yield of the anaerobic ammonia oxidation process is only about 15% of that of the general denitrification process, which reduces the sludge treatment cost.

[0005] As can be seen from the principle of anaerobic ammonia oxidation, in conventional wastewater, the anaerobic ammonia oxidation technology cannot be used alone, and nitrite must be provided by other denitrification processes. The existing combined processes include short-cut nitrification-anaerobic ammonia oxidation and short-cut denitrification-anaerobic ammonia oxidation. The principle is to use ammonia-oxidizing bacteria to convert ammonia to nitrite under aerobic conditions, use short-cut denitrifying bacteria to convert nitrate to nitrite under anoxic conditions, and then use anaerobic ammonia-oxidizing bacteria to convert the generated nitrite and ammonia in the wastewater to nitrogen gas under anoxic conditions. However, the above combined processes require strict conditions for denitrification (such as dissolved oxygen content in wastewater) when used alone. SUMMARY

[0006] In order to solve the technical problems of the existing nitrification-denitrification nitrogen removal method needing external carbon source, large aeration amount and sludge yield, and high cost, and the existing nitrogen removal method based on anaerobic ammonia oxidation requiring strict nitrogen removal conditions, the application provides a waste transfer station leachate advanced nitrogen removal method.The advanced nitrogen removal method can realize good cooperation between multiple nitrogen removal paths, has small dependence on carbon source, does not need external carbon source when performing waste transfer station leachate nitrogen removal, has small aeration amount and sludge yield, and has low requirement on nitrogen removal conditions.

[0007] The specific technical scheme of the application is as follows:

[0008] A waste transfer station leachate advanced nitrogen removal method comprises the following steps:

[0009] (1) passing wastewater into an anaerobic tank, and converting nitrate into nitrite and nitrogen by using denitrifying bacteria;

[0010] (2) passing the effluent of the anaerobic tank into an anoxic tank, converting nitrate into nitrite by using short-cut denitrifying bacteria, and converting nitrite and ammonia into nitrogen by using anaerobic ammonia oxidation bacteria;

[0011] (3) passing the effluent of the anoxic tank into an aerobic tank, converting ammonia into nitrite by using aerobic ammonia oxidation bacteria loaded on the outer layer of biological filler, and converting nitrite and ammonia into nitrogen by using anaerobic ammonia oxidation bacteria loaded on the inner layer of biological filler;

[0012] (4) passing the effluent of the aerobic tank into a membrane bioreactor, separating sludge and water, converting organic matter into water and carbon dioxide by using heterotrophic bacteria under aeration, and converting ammonia into nitrate by using aerobic ammonia oxidation bacteria and nitrite oxidation bacteria;

[0013] (5) partially refluxing the sludge-water mixture at the end of the aerobic tank into the anoxic tank;

[0014] (6) partially refluxing the sludge-water mixture in the membrane bioreactor into the anaerobic tank.

[0015] The method can fully utilize the biochemical action of aerobic and anaerobic ammonia oxidation bacteria, nitrite oxidation bacteria, denitrifying bacteria and other different microorganisms, can make nitrification-denitrification, short-cut nitrification-anaerobic ammonia oxidation, short-cut denitrification-anaerobic ammonia oxidation cooperate well, can avoid the defects of a single nitrogen removal path, can make the waste transfer station leachate with limited biodegradable organic matter content achieve a large degree of nitrogen removal under the condition of no external carbon source and small aeration amount and sludge yield, and the nitrogen removal effect is relatively small in the limitation of nitrogen removal conditions, so the requirement on the nitrogen removal conditions is low.

[0016] As preferred, in step (3), the outer layer of the biological filler is also loaded with nitrite oxidizing bacteria for converting nitrite into nitrate; and the inner layer of the biological filler is also loaded with denitrifying bacteria for converting nitrate into nitrite and nitrogen.

[0017] The nitrite oxidizing bacteria in the outer layer and the denitrifying bacteria in the inner layer of the biological filler in the aerobic tank can cooperate with other microorganisms in the whole deep denitrification process to further improve the denitrification effect of wastewater.

[0018] As preferred, in steps (1)-(3), the anaerobic tank, the anoxic tank and the aerobic tank all use the ribbon-type biological filler as the microbial carrier.

[0019] The ribbon-type biological filler (biological rope) is composed of a central rope bundle and a large number of fiber bundle rings radially distributed around the central rope bundle, which can solve the problems of sludge bulking and loss of suspended sludge with water flow, and has a large specific surface area, which is conducive to the attachment of functional bacteria on the biological filler to form a biofilm, and is conducive to the contact and mass transfer between the biofilm and wastewater.

[0020] As preferred, in step (3), the inner layer of the biological filler in the aerobic tank is loaded with monoamine oxidase, and the outer layer is not loaded with monoamine oxidase.

[0021] In the biological filler in the aerobic tank, the nitrite produced by the aerobic ammonia oxidizing bacteria in the outer layer can be quickly transferred to the anaerobic ammonia oxidizing bacteria in the inner layer, and the anaerobic ammonia oxidizing bacteria in the inner layer can help to reduce the toxicity of nitrite accumulation on the aerobic ammonia oxidizing bacteria. By this way, the aerobic and anaerobic ammonia oxidizing bacteria are integrated in the same biological filler, which is conducive to improving the denitrification effect.

[0022] However, although the aerobic ammonia oxidizing bacteria in the outer layer will consume oxygen, reducing the amount of oxygen entering the inner layer, the growth and anaerobic ammonia oxidation of anaerobic ammonia oxidizing bacteria require strict anaerobic conditions (studies have shown that the activity of anaerobic ammonia oxidizing bacteria will be inhibited only when 1 μmol / L of oxygen exists). Therefore, the present application loads monoamine oxidase in the inner layer of the biological filler, which can catalyze the conversion of organic amines in wastewater into ammonia under the action of oxygen, thereby reducing the content of organic amines in wastewater and providing ammonia for the anaerobic ammonia oxidizing bacteria in the inner layer, while consuming oxygen, further reducing the oxygen entering the inner layer of the biological filler and reducing the oxygen in the inner layer, thereby ensuring that the anaerobic ammonia oxidizing bacteria in the inner layer have high activity, can better convert nitrite and ammonia into nitrogen, and reduce the toxicity of nitrite accumulation on the aerobic ammonia oxidizing bacteria in the outer layer, thereby improving the denitrification effect of wastewater.

[0023] As preferred, in the biological filler in the aerobic tank, the diameter of the inner layer loaded with monoamine oxidase is 30-50% of the diameter of the biological filler.

[0024] Preferably, the method for preparing the biological filler in the aerobic tank comprises the following steps:

[0025] (A) The fiber bundle containing the terylene component is arranged in a serpentine shape, and is fixed in the center to form a plurality of primary fiber bundle rings radially distributed around the center rope bundle, to obtain a braided primary filler;

[0026] (B) After the primary filler is nitrated to introduce nitro groups, the introduced nitro groups are reduced to amino groups to obtain an amino-modified primary filler; (C) Monoamine oxidase is connected to the amino-modified primary filler by glutaraldehyde to obtain a monoamine oxidase-complexed primary filler; (D) According to the method in step (A), a plurality of secondary fiber bundle rings radially distributed around the center rope bundle are made on the monoamine oxidase-complexed primary filler using fiber bundles, to obtain a biological filler with a larger diameter than the primary filler.

[0027] The above process is based on the preparation method of conventional braided biological fillers, and the primary fiber bundle ring with a smaller diameter and the secondary fiber bundle ring with a larger diameter are combined to form a composite structure, with the primary fiber bundle ring located in the inner layer and the secondary fiber bundle ring located in the outer layer. Monoamine oxidase is loaded on the primary fiber bundle ring after the primary fiber bundle ring is prepared, thereby realizing the preparation of a biological filler with "monoamine oxidase loaded in the inner layer and no monoamine oxidase loaded in the outer layer". The monoamine oxidase loaded on the primary fiber bundle ring can effectively reduce the oxygen content in the inner layer and improve the activity of anaerobic monoamine oxidase in the inner layer.

[0028] Preferably, in steps (A) and (D), the linear mass ratio of the primary filler to the biological filler is 1:3-6.

[0029] Preferably, the specific process of step (B) comprises the following steps: after the primary filler is soaked in a nitric acid solution, it is taken out and reacted at 60-80℃ for 20-30 min, then washed, immersed in a reducing agent solution containing sodium sulfide and sodium carbonate, and reacted at 90-95℃ for 30-40 min, then taken out and washed, to obtain an amino-modified primary filler.

[0030] Further, in step (B), the concentration of the nitric acid solution is 1.0-2.5 wt%, and the concentrations of sodium sulfide and sodium carbonate in the reducing agent solution are 1.5-3.5 wt% and 1-4 wt%, respectively.

[0031] Further, in step (B), the mass ratio of the primary filler, the nitric acid solution, and the reducing agent solution is 1:30-50:80-120.

[0032] Further, in step (B), the soaking time is 20-40 min.

[0033] As preferred, the specific process of step (C) comprises the following steps: immersing the amino-functionalized primary filler into a glutaraldehyde solution, taking out and washing after 1-2 hours of soaking, immersing into a monoamine oxidase solution, reacting at 3-10℃ for 10-12 hours, taking out and washing, and obtaining the monoamine oxidase complexed primary filler.

[0034] Further, in step (C), the concentration of the glutaraldehyde solution is 5-10 wt%; and the concentration of the monoamine oxidase solution is 1-3 wt%.

[0035] Further, in steps (B) and (C), the mass ratio of the primary filler, the glutaraldehyde solution and the monoamine oxidase solution is 1:80-120:80-120.

[0036] As preferred, in step (1), the wastewater is stirred uniformly before being introduced into the anaerobic tank.

[0037] As preferred, in step (5), the backflow ratio of the sludge-water mixture at the end of the aerobic tank is 100-500%.

[0038] As preferred, in step (6), the backflow ratio of the sludge-water mixture in the membrane bioreactor is 50-150%.

[0039] As preferred, in steps (1)-(4), the dissolved oxygen content of the wastewater in the anaerobic tank is not higher than 0.2 mg / L, and the dissolved oxygen contents of the wastewater in the anoxic tank, the aerobic tank and the membrane bioreactor are 0.1-0.6 mg / L, 0.5-2.0 mg / L and 1-3 mg / L, respectively.

[0040] As preferred, in steps (1)-(3), the hydraulic retention times in the anaerobic tank, the anoxic tank and the aerobic tank are 2-4 h, 5-7 h and 8-14 h, respectively.

[0041] Compared with the prior art, the present application has the following advantages:

[0042] (1) The deep denitrification method of the present application can realize better cooperation among multiple denitrification pathways (including nitrification-denitrification, short-cut nitrification-anaerobic ammonium oxidation, short-cut denitrification-anaerobic ammonium oxidation, etc.), avoid the defects of a single denitrification pathway, and achieve a large degree of denitrification of landfill leachate from a garbage transfer station with limited content of biodegradable organic matter under the conditions of no additional carbon source and less aeration and sludge production, and has lower requirements for denitrification conditions.

[0043] (2) In this invention, braided biological packing is used as a microbial carrier in anaerobic, anoxic and aerobic tanks. Compared with suspended sludge process, functional bacteria can attach to the braided biological packing to form biofilm, which is not easy to cause sludge bulking and is not easy to be lost with water flow. In addition, the braided biological packing has a large specific surface area and porosity, which can provide more attachment points for microorganisms and reduce film formation time.

[0044] (3) In the aerobic tank, the present invention uses a biological packing material with an inner layer loaded with monoamine oxidase and an outer layer unloaded with monoamine oxidase. This can reduce the organic amine content in the wastewater and provide ammonia for the anaerobic ammonia oxidizing bacteria in the inner layer, while reducing the oxygen content in the inner layer, thereby improving the denitrification effect of the wastewater. Detailed Implementation

[0045] The present invention will be further described below with reference to embodiments.

[0046] General Implementation Examples

[0047] A method for deep denitrification of leachate from a waste transfer station includes the following steps:

[0048] (1) Wastewater is introduced into an anaerobic tank, where denitrifying bacteria convert nitrates into nitrites and nitrogen.

[0049] (2) The effluent from the anaerobic tank is introduced into the anoxic tank, where short-cut denitrifying bacteria are used to convert nitrates into nitrites, and anaerobic ammonia oxidizing bacteria are used to convert nitrites and ammonia into nitrogen.

[0050] (3) The effluent from the anoxic tank is introduced into the aerobic tank. The aerobic ammonia oxidizing bacteria loaded on the outer layer of the biological packing material convert ammonia into nitrite, and the anaerobic ammonia oxidizing bacteria loaded on the inner layer of the biological packing material convert nitrite and ammonia into nitrogen.

[0051] (4) The effluent from the aerobic tank is fed into the membrane bioreactor for mud-water separation. Under aeration, heterotrophic bacteria are used to convert organic matter into water and carbon dioxide, and aerobic ammonia oxidizing bacteria and nitrite oxidizing bacteria are used to convert ammonia into nitrate.

[0052] (5) Part of the mud-water mixture at the end of the aerobic tank is returned to the anoxic tank;

[0053] (6) Part of the mud-water mixture in the membrane bioreactor is returned to the anaerobic tank.

[0054] As a specific implementation method, in step (1): before introducing the wastewater into the anaerobic tank, it is stirred evenly.

[0055] In one specific implementation, in step (3): the outer layer of the biological packing is also loaded with nitrite-oxidizing bacteria, which are used to convert nitrite into nitrate; the inner layer of the biological packing is also loaded with denitrifying bacteria, which are used to convert nitrate into nitrite and nitrogen.

[0056] As a specific implementation method, in steps (1) to (3): braided biological packing material is used as a microbial carrier in the anaerobic tank, anoxic tank and aerobic tank.

[0057] In one specific implementation, in step (3): the inner layer of the biological packing material in the aerobic tank is loaded with monoamine oxidase, while the outer layer is not loaded with monoamine oxidase.

[0058] As one specific implementation method, the preparation method of the biological packing material in the aerobic tank includes the following steps:

[0059] (A) The fiber bundle containing polyester is serpentine and fixed in the center of the central rope bundle to form multiple primary fiber bundle loops that are radially distributed around the central rope bundle, thus obtaining a braided initial braided filler.

[0060] (B) After nitrifying the initial knitting packing to introduce nitro groups, the introduced nitro groups are reduced to amino groups to obtain aminated initial knitting packing; (C) Monoamine oxidase is linked to the aminated initial knitting packing via glutaraldehyde to obtain monoamine oxidase composite initial knitting packing; (D) Following the method in step (A), multiple secondary fiber bundle rings are made on the monoamine oxidase composite initial knitting packing using fiber bundles and arranged radially around the central rope bundle to obtain a biological packing with a diameter larger than that of the initial knitting packing.

[0061] In one specific embodiment, the inner layer of the biological packing material in the aerobic tank, which is loaded with monoamine oxidase, has a diameter of 30-50% of the diameter of the biological packing material; the ratio of the linear mass of the initial packing material to the biological packing material is 1:3-6.

[0062] In one specific embodiment, step (B) includes the following steps: The initial filler is soaked in a 1.0–2.5 wt% nitric acid solution for 20–40 min, then removed and reacted at 60–80°C for 20–30 min. After washing, it is immersed in a reducing agent solution containing 1.5–3.5 wt% sodium sulfide and 1–4 wt% sodium carbonate, reacted at 90–95°C for 30–40 min, removed, and washed to obtain an aminated initial filler. The mass ratio of the initial filler, nitric acid solution, and reducing agent solution is 1:30–50:80–120.

[0063] In one specific embodiment, step (C) includes the following steps: immersing the aminated pre-woven filler in a 5-10 wt% glutaraldehyde solution for 1-2 hours, then removing and washing it; subsequently immersing it in a 1-3 wt% monoamine oxidase solution and reacting it at 3-10°C for 10-12 hours; removing and washing it again to obtain the monoamine oxidase composite pre-woven filler. The mass ratio of the pre-woven filler, glutaraldehyde solution, and monoamine oxidase solution is 1:80-120:80-120.

[0064] As one specific implementation, in step (5): the reflux ratio of the mud-water mixture at the end of the aerobic tank is 100-500%.

[0065] In one specific implementation, in step (6): the reflux ratio of the mud-water mixture in the membrane bioreactor is 50-150%.

[0066] As a specific implementation method, in steps (1) to (4): the dissolved oxygen content of the wastewater in the anaerobic tank is not higher than 0.2 mg / L, and the dissolved oxygen content of the wastewater in the anoxic tank, aerobic tank and membrane bioreactor is 0.1 to 0.6, 0.5 to 2.0 and 1 to 3 mg / L, respectively.

[0067] In one specific implementation, in steps (1) to (3), the hydraulic retention times in the anaerobic tank, the anoxic tank, and the aerobic tank are 2 to 4 hours, 5 to 7 hours, and 8 to 14 hours, respectively.

[0068] Example 1

[0069] The experimental water was taken from the leachate after anaerobic digestion at a waste transfer station in Zhejiang Province. The water quality was as follows: CODcr 3000–3500 mg / L, BOD5 500–700 mg / L, NH4+ + -N is 190–210 mg / L, and organic nitrogen is 30–40 mg / L.

[0070] The above leachate undergoes deep denitrification, and the specific process is as follows:

[0071] (1) Braided biological packing material (80 mm in diameter, 65 g / m in linear mass, and made of polyester filament and expanded long filament BCF blend) was used in the anaerobic, anoxic, and aerobic tanks, with a packing filling rate of 40%. Mature sludge from the landfill leachate treatment plant was added to the anaerobic, anoxic, aerobic, and membrane bioreactors at a concentration of 4000 mg / L for acclimatization and biofilm formation. After acclimatization and biofilm formation, denitrifying bacteria were attached to the braided biological packing material in the anaerobic tank, short-range denitrifying bacteria and anaerobic ammonia oxidizing bacteria were attached to the braided biological packing material in the anoxic tank, aerobic ammonia oxidizing bacteria and nitrite oxidizing bacteria were attached to the outer layer of the braided biological packing material in the aerobic tank, and anaerobic ammonia oxidizing bacteria and denitrifying bacteria were attached to the inner layer. Heterotrophic bacteria, aerobic ammonia oxidizing bacteria and nitrite oxidizing bacteria were present in the membrane bioreactor.

[0072] (2) After the acclimatization and biofilm formation are completed, the leachate is introduced into the raw water tank and stirred to stabilize the quality of the biochemical influent.

[0073] (3) The effluent from the raw water tank is introduced into the anaerobic tank. The dissolved oxygen content of the wastewater in the tank is maintained at a level not higher than 0.2 mg / L. The denitrifying bacteria are used to convert nitrate into nitrite and nitrogen. The hydraulic retention time of the tank is set to 3 hours.

[0074] (4) The effluent from the anaerobic tank is introduced into the anoxic tank. The dissolved oxygen content of the wastewater in the tank is maintained at 0.35±0.25mg / L. Short-range denitrifying bacteria are used to convert nitrate into nitrite, and anaerobic ammonia oxidizing bacteria are used to convert nitrite and ammonia into nitrogen. The hydraulic retention time of the tank is set to 6h.

[0075] (5) The effluent from the anoxic tank is introduced into the aerobic tank. The dissolved oxygen content of the wastewater in the tank is controlled to be 1.25±0.75mg / L by aeration. The aerobic ammonia oxidizing bacteria and nitrite oxidizing bacteria loaded on the outer layer of the biological packing are used to convert ammonia into nitrite and nitrite into nitrate, respectively. The anaerobic ammonia oxidizing bacteria and denitrifying bacteria loaded on the inner layer of the biological packing are used to convert nitrite and ammonia into nitrogen gas and nitrate into nitrite and nitrogen gas, respectively. The hydraulic retention time of the tank is set to 11h.

[0076] (6) The mud-water mixture at the end of the aerobic tank is returned to the anoxic tank at a 250% return ratio. The effluent from the aerobic tank is fed into the membrane bioreactor for mud-water separation. The dissolved oxygen content of the wastewater in the membrane bioreactor is controlled to be 2±1 mg / L by aeration. Heterotrophic bacteria are used to convert organic matter into water and carbon dioxide, and aerobic ammonia oxidizing bacteria and nitrite oxidizing bacteria are used to convert ammonia into nitrate.

[0077] (7) The sludge-water mixture in the membrane bioreactor was refluxed back to the anaerobic tank at a 100% reflux ratio. The effluent from the membrane bioreactor ultimately entered the effluent tank. During 30 days of stable operation, the water quality in the effluent tank was continuously monitored, and the measured CODcr was 200–250 mg / L, BOD5 was 30–50 mg / L, and NH4+ was [missing value]. + -N is 5.0–15 mg / L, and organic nitrogen is 10–20 mg / L.

[0078] Example 2

[0079] The only difference between this embodiment and Embodiment 1 is that the inner layer of the braided biological packing material in the aerobic tank is loaded with monoamine oxidase. The preparation method of this packing material is as follows:

[0080] (A) Using the conventional braided biological filler weaving method, the initial braided filler is made by weaving a fiber bundle of polyester filament and bulked filament BCF in a serpentine pattern and fixing it in the center with a central rope bundle to form multiple primary fiber bundle rings that are radially distributed around the central rope bundle as the axis, thus obtaining a braided initial braided filler with a diameter of 40 mm and a thread weight of 15 g / m.

[0081] (B) Take a 1.5wt% nitric acid solution with a mass of 40 times that of the initial knitting filler, immerse the initial knitting filler in the solution, soak for 30 minutes, remove it, keep it at 70℃ for 25 minutes, and wash it with clean water to obtain nitrated initial knitting filler. Dissolve sodium sulfide and sodium carbonate in water to prepare a reducing agent solution with a mass of 100 times that of the initial knitting filler, wherein the concentrations of sodium sulfide and sodium carbonate are 2.5wt% and 3wt%, respectively. Immerse the nitrated initial knitting filler in the solution, keep it at 90℃ for 35 minutes, remove it, wash it with clean water, and dry it to obtain aminated initial knitting filler.

[0082] (C) Glutaraldehyde was dissolved in water to prepare a solution with a mass of 100 times that of the primary knitting filler and a concentration of 8 wt%. The aminated primary knitting filler was immersed in the solution for 1.5 h, then removed and washed with water to obtain glutaraldehyde-modified primary knitting filler. Monoamine oxidase was dissolved in pyridine buffer to prepare an enzyme solution with a mass of 100 times that of the primary knitting filler and a concentration of 2 wt%. The glutaraldehyde-modified primary knitting filler was immersed in the solution and placed at 4 °C for 10 h. Then it was removed, washed with water, and dried to obtain monoamine oxidase composite primary knitting filler.

[0083] (D) Following the method in step (A), multiple secondary fiber bundle rings are made of fiber bundles woven from polyester filaments and bulky filaments BCF on the monoamine oxidase composite primary braided filler, with the primary fiber bundle rings located in the inner layer and the secondary fiber bundle rings located in the outer layer, to obtain a braided biological filler with a diameter of 80 mm and a linear mass of 50 g / m.

[0084] In this embodiment, except for the braided biological packing material used in the aerobic tank, everything else is the same as in Example 1. The experimental water is from the same batch as in Example 1 (same source and water quality). During 30 days of stable operation, the water quality in the effluent tank was continuously monitored, and the CODcr was measured to be 180–205 mg / L, BOD5 to 25–35 mg / L, and NH4+ to be... + -N is 0.08–2.5 mg / L, and organic nitrogen is 2.0–6.0 mg / L.

[0085] Example 3

[0086] The only difference between this embodiment and Embodiment 1 is that the inner layer of the braided biological packing material in the aerobic tank is loaded with monoamine oxidase. The preparation method of this packing material is as follows:

[0087] (A) Using the conventional braided biological filler weaving method, the initial braided filler is made by weaving a fiber bundle of polyester filament and bulked filament BCF in a serpentine pattern and fixing it in the center with a central rope bundle to form multiple primary fiber bundle rings that are radially distributed around the central rope bundle as the axis, thus obtaining a braided initial braided filler with a diameter of 40 mm and a thread weight of 15 g / m.

[0088] (B) Take a 2.5wt% nitric acid solution with a mass of 30 times that of the initial knitting filler, immerse the initial knitting filler in the solution, soak for 20 minutes, remove it, keep it at 60℃ for 30 minutes, and wash it with clean water to obtain nitrated initial knitting filler. Dissolve sodium sulfide and sodium carbonate in water to prepare a reducing agent solution with a mass of 80 times that of the initial knitting filler, wherein the concentrations of sodium sulfide and sodium carbonate are 3.5wt% and 4wt%, respectively. Immerse the nitrated initial knitting filler in the solution, keep it at 90℃ for 40 minutes, remove it, wash it with clean water, and dry it to obtain aminated initial knitting filler.

[0089] (C) Glutaraldehyde was dissolved in water to prepare a solution with a mass of 80 times that of the primary filler and a concentration of 10 wt%. The aminated primary filler was immersed in the solution for 1 hour, then removed and washed with water to obtain glutaraldehyde-modified primary filler. Monoamine oxidase was dissolved in pyridine buffer to prepare an enzyme solution with a mass of 80 times that of the primary filler and a concentration of 3 wt%. The glutaraldehyde-modified primary filler was immersed in the solution and placed at 4°C for 10 hours. Then it was removed, washed with water, and dried to obtain monoamine oxidase composite primary filler.

[0090] (D) Following the method in step (A), multiple secondary fiber bundle rings are made of fiber bundles woven from polyester filaments and bulky filaments BCF on the monoamine oxidase composite primary braided filler, with the primary fiber bundle rings located in the inner layer and the secondary fiber bundle rings located in the outer layer, to obtain a braided biological filler with a diameter of 80 mm and a linear mass of 50 g / m.

[0091] In this embodiment, except for the braided biological packing material used in the aerobic tank, everything else is the same as in Example 1. The experimental water is from the same batch as in Example 1 (same source and water quality). During 30 days of stable operation, the water quality in the effluent tank was continuously monitored, and the CODcr was measured to be 165–200 mg / L, BOD5 to 20–45 mg / L, and NH4+ to be... + -N is 0.05–4.0 mg / L, and organic nitrogen is 2.5–8.0 mg / L.

[0092] Example 4

[0093] The only difference between this embodiment and Embodiment 1 is that the inner layer of the braided biological packing material in the aerobic tank is loaded with monoamine oxidase. The preparation method of this packing material is as follows:

[0094] (A) Using the conventional braided biological filler weaving method, the initial braided filler is made by weaving a fiber bundle of polyester filament and bulked filament BCF in a serpentine pattern and fixing it in the center with a central rope bundle to form multiple primary fiber bundle rings that are radially distributed around the central rope bundle as the axis, thus obtaining a braided initial braided filler with a diameter of 40 mm and a thread weight of 15 g / m.

[0095] (B) Take a 1.0 wt% nitric acid solution with a mass of 50 times that of the initial knitting filler, immerse the initial knitting filler in the solution, soak for 40 minutes, remove it, keep it at 80℃ for 20 minutes, and wash it with clean water to obtain nitrated initial knitting filler. Dissolve sodium sulfide and sodium carbonate in water to prepare a reducing agent solution with a mass of 120 times that of the initial knitting filler, wherein the concentrations of sodium sulfide and sodium carbonate are 1.5 wt% and 1 wt%, respectively. Immerse the nitrated initial knitting filler in the solution, keep it at 95℃ for 30 minutes, remove it, wash it with clean water, and dry it to obtain aminated initial knitting filler.

[0096] (C) Glutaraldehyde was dissolved in water to prepare a solution with a mass of 120 times that of the primary knitting filler and a concentration of 5 wt%. The aminated primary knitting filler was immersed in the solution for 2 hours, then removed and washed with water to obtain glutaraldehyde-modified primary knitting filler. Monoamine oxidase was dissolved in pyridine buffer to prepare an enzyme solution with a mass of 120 times that of the primary knitting filler and a concentration of 1 wt%. The glutaraldehyde-modified primary knitting filler was immersed in the solution and placed at 4°C for 12 hours. Then it was removed, washed with water, and dried to obtain monoamine oxidase composite primary knitting filler.

[0097] (D) Following the method in step (A), multiple secondary fiber bundle rings are made of fiber bundles woven from polyester filaments and bulky filaments BCF on the monoamine oxidase composite primary braided filler, with the primary fiber bundle rings located in the inner layer and the secondary fiber bundle rings located in the outer layer, to obtain a braided biological filler with a diameter of 80 mm and a linear mass of 50 g / m.

[0098] In this embodiment, except for the braided biological packing material used in the aerobic tank, everything else is the same as in Example 1. The experimental water is from the same batch as in Example 1 (same source and water quality). During 30 days of stable operation, the water quality in the effluent tank was continuously monitored, and the CODcr was measured to be 185–215 mg / L, BOD5 to 30–40 mg / L, and NH4 to be [missing information]. + -N is 0.1–2.5 mg / L, and organic nitrogen is 5.0–10 mg / L.

[0099] Data Analysis: Compared to Example 1, the ammonia nitrogen and organic nitrogen content in the effluent of Examples 2-4 were significantly reduced. This is because, in Examples 2-4, monoamine oxidase was loaded into the inner layer of the braided biological packing material in the aerobic tank. This enzyme can catalyze the conversion of organic amines in wastewater into ammonia under the action of oxygen. Therefore, it can reduce the organic amine content in the wastewater and provide ammonia for the anaerobic ammonia oxidizing bacteria in the inner layer, while consuming oxygen. This further reduces the amount of oxygen entering the inner layer of the biological packing material and reduces the amount of oxygen in the inner layer, thereby ensuring that the anaerobic ammonia oxidizing bacteria in the inner layer have high activity. They can better convert nitrite and ammonia into nitrogen gas and reduce the toxicity of nitrite accumulation to the aerobic ammonia oxidizing bacteria in the outer layer, thus improving the denitrification effect of wastewater.

[0100] Comparative Example 1

[0101] The only difference between this comparative example and Example 2 is that the braided biological packing material in the aerobic tank has monoamine oxidase loaded on both the inner and outer layers. The preparation method of this packing material is as follows:

[0102] (A) Using the conventional braided biological filler weaving method, the initial braided filler is made by weaving a fiber bundle of polyester filament and bulked filament BCF in a serpentine pattern and fixing it in the center with a central rope bundle to form multiple primary fiber bundle rings that are radially distributed around the central rope bundle as the axis, thus obtaining a braided initial braided filler with a diameter of 40 mm and a thread weight of 15 g / m.

[0103] (B) Following the method in step (A), on the monoamine oxidase composite primary knitting filler, multiple secondary fiber bundle rings are made of fiber bundles woven from polyester filaments and bulky filaments BCF, arranged radially around the central rope bundle, so that the primary fiber bundle rings are located in the inner layer and the secondary fiber bundle rings are located in the outer layer, to obtain unmodified biological filler with a diameter of 80 mm and a linear mass of 50 g / m.

[0104] (C) Take a 1.5wt% nitric acid solution with a mass of 40 times that of the unmodified biological packing material, immerse the unmodified biological packing material in the solution, soak for 30 minutes, remove it, keep it at 70℃ for 25 minutes, and wash it with clean water to obtain nitrated packing material. Dissolve sodium sulfide and sodium carbonate in water to prepare a reducing agent solution with a mass of 100 times that of the unmodified biological packing material, wherein the concentrations of sodium sulfide and sodium carbonate are 2.5wt% and 3wt%, respectively. Immerse the nitrated packing material in the solution, keep it at 90℃ for 35 minutes, remove it, wash it with clean water, and dry it to obtain aminated packing material.

[0105] (D) Glutaraldehyde was dissolved in water to prepare a solution with a concentration of 8 wt%, which was 100 times that of the unmodified biological packing. The aminated packing was immersed in the solution for 1.5 h, then removed and washed with water to obtain glutaraldehyde-modified packing. Monoamine oxidase was dissolved in pyridine buffer to prepare an enzyme solution with a concentration of 2 wt%, which was 100 times that of the unmodified biological packing. The glutaraldehyde-modified packing was immersed in the solution and placed at 4 °C for 10 h. Then it was removed, washed with water, and dried to obtain braided biological packing.

[0106] In this comparative example, except for the braided biological packing material used in the aerobic tank, everything else was the same as in Example 2. The experimental water was from the same batch as in Example 2 (same source and water quality). During 30 days of stable operation, the water quality in the effluent tank was continuously monitored, and the CODcr was measured to be 150–180 mg / L, BOD5 to 15–30 mg / L, and NH4+ to be... + -N is 8.5–17 mg / L, and organic nitrogen is 0.5–4.0 mg / L.

[0107] Data analysis: Compared with Example 2, although Comparative Example 1 increased the loading of monoamine oxidase, the ammonia nitrogen content in the effluent was higher (even slightly higher than that in Example 1 without monoamine oxidase loading). This is because the monoamine oxidase loaded in the outer layer consumes oxygen, which inhibits aerobic ammonia oxidation and leads to a decrease in the overall denitrification effect.

[0108] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0109] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for deep denitrification of leachate from a waste transfer station, characterized in that, Includes the following steps: (1) The wastewater is introduced into the anaerobic tank, and denitrifying bacteria are used to convert nitrates into nitrites and nitrogen. (2) The effluent from the anaerobic tank is introduced into the anoxic tank, and short-cut denitrifying bacteria are used to convert nitrate into nitrite, and anaerobic ammonia oxidizing bacteria are used to convert nitrite and ammonia into nitrogen. (3) The effluent from the anoxic tank is introduced into the aerobic tank. The aerobic ammonia oxidizing bacteria loaded on the outer layer of the biological packing convert ammonia into nitrite, and the anaerobic ammonia oxidizing bacteria loaded on the inner layer of the biological packing convert nitrite and ammonia into nitrogen. The inner layer of the biological packing is loaded with monoamine oxidase, and the outer layer is not loaded with monoamine oxidase. The preparation steps include: preparing a primary packing consisting of a central rope bundle and multiple primary fiber bundle rings radially distributed around it; after nitrification to introduce nitro groups, the nitro groups are reduced to amino groups; monoamine oxidase is linked to the amino group through glutaraldehyde; and multiple secondary fiber bundle rings radially distributed around the central rope bundle are made by fiber bundles to obtain a biological packing with a diameter larger than that of the primary packing. (4) The effluent from the aerobic tank is fed into the membrane bioreactor for mud-water separation. Under aeration, heterotrophic bacteria are used to convert organic matter into water and carbon dioxide, and aerobic ammonia oxidizing bacteria and nitrite oxidizing bacteria are used to convert ammonia into nitrate. (5) Part of the mud-water mixture at the end of the aerobic tank is returned to the anoxic tank; (6) Part of the mud-water mixture in the membrane bioreactor is returned to the anaerobic tank.

2. The deep denitrification method as described in claim 1, characterized in that, In step (3): the outer layer of the biological packing is also loaded with nitrite-oxidizing bacteria, which are used to convert nitrite into nitrate; the inner layer of the biological packing is also loaded with denitrifying bacteria, which are used to convert nitrate into nitrite and nitrogen.

3. The deep denitrification method as described in claim 1, characterized in that, In the aerobic tank, the inner layer of the biological packing material loaded with monoamine oxidase has a diameter of 30-50% of the diameter of the biological packing material.

4. The deep denitrification method as described in claim 1 or 3, characterized in that, The preparation method of the biological packing material in the aerobic tank specifically includes the following steps: (A) The fiber bundle containing polyester is serpentine and fixed in the center of the central rope bundle to form multiple primary fiber bundle loops that are radially distributed around the central rope bundle, thus obtaining a braided initial braided filler. (B) After nitrifying the initial filler to introduce nitro groups, the introduced nitro groups are reduced to amino groups to obtain aminated initial filler; (C) Monoamine oxidase is linked to aminated primary knitting filler via glutaraldehyde to obtain monoamine oxidase composite primary knitting filler; (D) Following the method in step (A), multiple secondary fiber bundle rings are made of fiber bundles on the monoamine oxidase composite primary filler, which are radially distributed with the central rope bundle as the axis, to obtain a biological filler with a diameter larger than that of the primary filler.

5. The deep denitrification method as described in claim 1, characterized in that, In step (1): Before introducing the wastewater into the anaerobic tank, stir it evenly.

6. The deep denitrification method as described in claim 1, characterized in that, In step (5): the reflux ratio of the mud-water mixture at the end of the aerobic tank is 100~500%.

7. The deep denitrification method as described in claim 1, characterized in that, In step (6): the reflux ratio of the mud-water mixture in the membrane bioreactor is 50-150%.

8. The deep denitrification method as described in claim 1, characterized in that, In steps (1) to (4): the dissolved oxygen content of the wastewater in the anaerobic tank is not higher than 0.2 mg / L, and the dissolved oxygen content of the wastewater in the anoxic tank, aerobic tank and membrane bioreactor is 0.1~0.6, 0.5~2.0 and 1~3 mg / L, respectively.

9. The deep denitrification method as described in claim 1, characterized in that, In steps (1) to (3), the hydraulic retention times in the anaerobic tank, anoxic tank, and aerobic tank are 2-4h, 5-7h, and 8-14h, respectively.