Multistage AO process method for dephosphorization and denitrification of sewage

Abstract

The invention relates to the field of sewage treatment, and provides a multistage AO process method for dephosphorization and denitrification of sewage, which comprises the following steps: water sequentially flows through an anoxic zone I, an anaerobic zone, an aerobic zone-anoxic zone II and a settling zone; the different areas are communicated through gaps, and the gaps of the adjacent areas are staggered up and down; spiral biological stuffing is suspended in the anoxic zone I and the aerobic zone. The notches of the adjacent areas are staggered up and down, so that water flows through the areas in an S shape, the contact time is prolonged in a limited space, and the sewage treatment effect is improved.

Description

Technical Field

[0001] The invention relates to the field of sewage treatment, and in particular to a multi-stage AO process method for removing phosphorus and nitrogen from sewage. Background Art

[0002] The multi-stage AO process has become one of the important technologies in the field of sewage treatment. The process uses multi-stage contact oxidation (AO) technology to treat wastewater, achieving efficient phosphorus removal and nitrogen removal effects. For example, patent CN112607862A discloses a multi-stage AO sewage biochemical treatment process: including a first-stage sewage biochemical treatment unit, a second-stage sewage biochemical treatment unit, and a third-stage sewage biochemical treatment unit connected in series in the direction of the sewage treatment process, wherein the first-stage sewage biochemical treatment unit includes an anaerobic tank, an anoxic tank, an aerobic tank, and an internal recirculation zone connected in sequence, and the second-stage sewage biochemical treatment unit and the third-stage sewage biochemical treatment unit both include an anoxic / anaerobic tank, an aerobic tank, and an internal recirculation zone connected in sequence. The invention forms a multi-stage A / O operation process with a concentration gradient through an alternating combination of anaerobic, anoxic, and aerobic, deepens the removal of organic matter, strengthens biological nitrogen and phosphorus removal, and especially strengthens biological denitrification, achieving high-quality effluent while reducing sludge. However, there are many pools and treatment units, which occupy a large area and are costly. Therefore, an ideal solution is needed. Summary of the invention

[0003] The present invention provides a multi-stage AO process method for removing phosphorus and nitrogen from sewage. The gaps in adjacent zones are staggered up and down so that water flows through each zone in an S shape, prolonging the contact time in a limited space and improving the sewage treatment effect.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: A multi-stage AO process method for removing phosphorus and nitrogen from sewage, water flows through anoxic zone one, anaerobic zone, aerobic zone-anoxic zone two and sedimentation zone in sequence; different zones are connected by gaps, and the gaps of adjacent zones are arranged alternately up and down; spiral biological fillers are suspended in anoxic zone one and aerobic zone.

[0005] Preferably, there are at least two aerobic zone-anoxic zone IIs, which are arranged in series.

[0006] Preferably, the spiral biological filler comprises a middle rope and a filler rope spirally wound on the middle rope, the filler rope is a modified glass fiber, and the preparation method of the modified glass fiber is: (1) adding an octahydroxy cage-shaped silsesquioxane monomer to an acrylic emulsion containing an acrylic monomer to obtain a uniform mixture; the mass of the octahydroxy cage-shaped silsesquioxane monomer is 0.5-2% of the mass of the emulsion; (2) The glass fiber is immersed in the mixture of (1), taken out, and solidified into a shape.

[0007] Preferably, the components of the acrylic emulsion are: acrylic monomer, initiator, emulsifier, ethanol and water, the solid content of the acrylic emulsion is 1-3%; the mass of the initiator is 2-6% of the acrylic monomer, and the mass of the emulsifier is 5-8% of the acrylic monomer.

[0008] Preferably, the particle size of the acrylic emulsion is 30-50 nm.

[0009] Preferably, the immersion time is 6-14 hours; the curing conditions are: drying at 80-100° C. for 20-60 minutes.

[0010] Preferably, anaerobic activated sludge is provided in the anaerobic zone, and facultative activated sludge is provided in the anoxic zone 2.

[0011] Preferably, a vertical flow tube is provided in the center of the sedimentation zone, and a hexagonal honeycomb inclined tube filler is provided between the sedimentation zone and the vertical flow tube.

[0012] Preferably, an air aeration device is provided at the bottom of the anoxic zone; and an oxygen aeration device is provided at the bottom of the aerobic zone.

[0013] Therefore, the beneficial effects of the present invention are as follows: the water quality flowing out of the sedimentation area outlet meets the standards for CODcr, BOD5, ammonia nitrogen, SS and other indicators while achieving the standard discharge of total nitrogen and total phosphorus; the total nitrogen removal rate is ≥85%, the total phosphorus removal rate is ≥90%, and the treated water quality compliance rate is 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a flow chart of the multi-stage AO process for removing phosphorus and nitrogen from sewage.

[0015] In the figure: 1, anoxic zone one, 11, air aeration device, 2, anaerobic zone, 21, anaerobic activated sludge, 3, aerobic zone, 31, oxygen aeration device, 4, anoxic zone two, 41, facultative anaerobic activated sludge, 5, partition, 6, gap, 7, sedimentation zone, 71, vertical flow tube, 72, hexagonal honeycomb inclined tube packing, 73, water outlet, 74, mud outlet, 8, spiral biological packing, 81, middle rope, 82, packing rope. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further described below through specific embodiments.

[0017] In the present invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the art. The methods in the embodiments, unless otherwise specified, are all conventional methods in the art. Unless otherwise specified, parts are all weight parts, temperatures are expressed in ° C or at ambient temperature, and pressures are atmospheric pressure or near atmospheric pressure. There are many variations and combinations of reaction conditions (such as component concentrations, desired solvents, solvent mixtures, temperatures, pressures, and other reaction ranges) and conditions that can be used to optimize the purity and yield of the product obtained by the method, and only reasonable routine experiments will be required to optimize such method conditions.

[0018] Example A multi-stage AO process for removing phosphorus and nitrogen from sewage, water flows through anoxic zone 1, anaerobic zone, aerobic zone-anoxic zone 2 and sedimentation zone in sequence, and there are at least two aerobic zone-anoxic zone 2, which are arranged in series. Different zones are connected by gaps, and the gaps of adjacent zones are arranged in an up-and-down staggered manner, so that water can flow through each zone in an S shape, prolonging the contact time in a limited space and improving the sewage treatment effect.

[0019] A spiral biological filler is suspended in the anoxic zone, and an air aeration device is provided at the bottom. The spiral biological filler consists of a middle rope and a filler rope spirally wound on the middle rope. The spiral structure makes the filler have a large specific surface area, which can ensure sufficient biofilm space and sufficient biomass in practical applications. The air aeration device at the bottom can increase the flow of water and increase the contact between sewage and spiral biological filler. The three-dimensional spiral biological filler has a large opening flow channel, which can reduce the flow resistance during tumbling and rotation, and has good water permeability and water flow, which can maintain a high flow rate and realize material exchange and energy exchange.

[0020] Anaerobic activated sludge is set up in the anaerobic zone. Activated sludge is formed by the mixing of microbial communities such as bacteria, fungi, protozoa, metazoa, etc. with suspended matter and colloidal substances in sewage. It has a strong ability to adsorb and decompose organic matter and good sedimentation performance. It is called activated sludge because of its biochemical activity. The complex microorganisms in the activated sludge and the organic nutrients in the wastewater form a complex food chain. The first to undertake the purification task are heterotrophic bacteria and saprophytic fungi. Bacteria, especially spherical bacteria, play the most critical role. The activated sludge with good operation is a bacterial floc composed of spherical bacteria with filamentous bacteria as the skeleton. It has good sedimentation. With the normal operation of the activated sludge, bacteria multiply in large numbers and begin to grow protozoa, which are primary predators of bacteria. Common protozoa in activated sludge are flagellates, caterpillars, ciliates and sucrose worms. When the activated sludge matures, fixed ciliates and seed worms dominate; metazoans are secondary predators of bacteria, such as rotifers and nematodes, which can only appear when the dissolved oxygen is sufficient, so the appearance of metazoans indicates that the treated water quality has improved.

[0021] A spiral biological filler is suspended in the aerobic zone, and an oxygen aeration device is provided at the bottom. The spiral biological filler is also composed of a middle rope and a filler rope spirally wound around the middle rope. The oxygen aeration device provides a continuous supply of oxygen to the aerobic zone.

[0022] Anoxic zone 2 is equipped with facultative anaerobic activated sludge. Under anaerobic conditions, facultative anaerobic microorganisms degrade the macromolecular organic matter that is difficult to degrade in the wastewater, improve the biodegradability of the wastewater, and significantly improve the aerobic degradation performance in the later stage.

[0023] A vertical flow tube is set in the center of the sedimentation area, and a hexagonal honeycomb oblique tube filler is set between the sedimentation area and the vertical flow tube. The hexagonal honeycomb oblique tube filler is designed and developed based on the "shallow sedimentation" theory. The filler has a large wet perimeter, a small hydraulic radius, a good laminar flow state during operation, and the particle sedimentation is not disturbed by turbulence. It can accelerate the separation of particles and water and shorten the sedimentation distance of particles.

[0024] Based on GB18918-2002 "Pollutant Discharge Standard for Urban Sewage Treatment Plants", the water quality flowing out of the sedimentation area outlet of the present invention meets the standards for CODcr, BOD5, ammonia nitrogen, SS and other indicators while achieving the standard discharge of total nitrogen and total phosphorus. The total nitrogen removal rate is ≥85%, the total phosphorus removal rate is ≥90%, and the treated water quality compliance rate is 100%.

[0025] In order to improve the sewage treatment effect, the present invention further improves the packing rope. The packing rope is generally made of polyester and polypropylene, but it cannot have both mechanical properties and biological affinity. The present invention uses polypropylene containing octahydroxy cage silsesquioxane monomer to coat glass fiber to obtain modified glass fiber. The packing rope made of modified glass fiber has high biological affinity, can increase the biomass adsorbed on the rope, and significantly prolongs the service life, reducing the replacement cost.

[0026] The preparation method of modified glass fiber is: (1) Preparation of acrylic emulsion With acrylic acid as monomer, ethanol and water as dispersion medium, under the action of initiator and emulsifier, an acrylic emulsion with a particle size of 30-50nm is prepared. The mass of the initiator is 2-6% of the acrylic monomer, and the mass of the emulsifier is 5-8% of the acrylic monomer. The particle size of the emulsion can be controlled by adjusting the ratio of the emulsifier and the amount of seed.

[0027] The specific preparation method of acrylic emulsion can adopt any existing technology, as long as the particle size is guaranteed to be 30-50nm. For example, the following steps are adopted in the embodiment: emulsifier Span 80 and sodium allyloxyhydroxypropane sulfonate are added to an ethanol aqueous solution with a volume ratio of 1:1, and heated to 70°C while stirring; acrylic monomer and initiator AIBN are dissolved in ethanol, and added dropwise to the above heating system together with an initiator K2S2O8 aqueous solution, and kept at 70°C for 5h; cooled to room temperature to obtain acrylic emulsion.

[0028] (2) diluting the acrylic emulsion obtained in step (1) to a solid content of 1-3%, adding 0.5-2% by weight of the acrylic emulsion of octahydroxy cage-shaped silsesquioxane monomer, and dispersing to obtain a uniform mixture. The octahydroxy cage-shaped silsesquioxane monomer is an octapolysilsesquioxane in which all eight end groups contain hydroxyl groups, such as the structure disclosed in patent CN103214510B.

[0029] (3) The glass fiber is immersed in the mixture of (2) for 6-14 hours, then taken out, dried at 80-100° C. for 20-60 minutes to solidify and shape, thereby obtaining a modified glass fiber.

[0030] Glass fiber has the advantages of strong heat resistance, good corrosion resistance, and high mechanical strength. There are active groups such as amino and hydroxyl groups on the surface of glass fiber. Octahydroxy cage silsesquioxane monomer is cross-linked with acrylic acid to form a network structure. There are deep grooves on the surface of uncoated glass fiber, and the grooves are distributed relatively evenly; the grooves on the surface of glass fiber coated with octahydroxy cage silsesquioxane monomer and acrylic acid do not disappear, the depth of the grooves becomes shallower, and the distribution on the surface of glass fiber is relatively uniform. There is no phenomenon of agglomeration of impregnated components on the surface of glass fiber and the coating filling the grooves. These grooves can play an anchoring role when they interact with polyacrylic acid.

[0031] Example 1 A multi-stage AO process for removing phosphorus and nitrogen from sewage, such as Figure 1As shown, the sewage passes through the anoxic zone 1, the anaerobic zone 2, the aerobic zone 3, the anoxic zone 24, the second aerobic zone 3, the second anoxic zone 24 and the sedimentation zone 7 in sequence. Different zones are separated by a partition 5, and a notch 6 is provided on the partition 5. Different zones are connected through the notch 6, and the notches 6 of adjacent zones are arranged in an up-and-down staggered manner. Water can flow through each zone in an S shape, prolonging the contact time in a limited space and improving the sewage treatment effect. Among them, a spiral biological filler 8 is suspended in the middle of the anoxic zone 1, and an air aeration device 11 is provided at the bottom; the spiral biological filler 8 is composed of a middle rope 81 and a filler rope 82 spirally wound on the middle rope 81, and the filler rope 82 is a commercially available polypropylene filler rope. Anaerobic activated sludge 21 is provided in the anaerobic zone 2, which is also equipped with an aeration device (not shown in the figure). A spiral biological filler 8 is also suspended in the middle of the aerobic zone 3, but the adsorbed organisms are different from those in the anoxic zone 1; and an oxygen aeration device 31 is provided at the bottom. The anoxic zone 2 4 is provided with anoxic activated sludge 41, which is also equipped with an aeration device (not shown in the figure). The structures of the second aerobic zone 3 and the second anoxic zone 2 4 are exactly the same as those of the aerobic zone 3 and the anoxic zone 2 4. In practical applications, more groups of aerobic zones 3 and anoxic zones 2 4 can be set in series. A vertical flow tube 71 is provided at the axial center of the sedimentation zone 7, and a hexagonal honeycomb inclined tube filler 72 is provided between the sedimentation zone 7 and the vertical flow tube 71. A water outlet 73 is provided above the side wall of the sedimentation zone 7 for the treated water to flow out; the bottom of the sedimentation zone 7 is in an inverted cone shape, which is conducive to sludge enrichment, and a mud outlet 74 is provided at the bottom, and the sludge can be transported back to the anaerobic zone 2 or the anoxic zone 2 4 for recycling.

[0032] Example 2 The difference from Embodiment 1 is that the filler rope 82 is modified glass fiber.

[0033] The preparation method of the modified glass fiber is as follows: (1) Preparation of acrylic emulsion With acrylic acid as monomer, ethanol and water as dispersion medium, initiator (AIBN and K2S2O8), emulsifier (Span80 and sodium allyloxyhydroxypropane sulfonate) were used to prepare acrylic emulsion with particle size of 30-50nm. The mass of initiator was 4% of acrylic acid monomer, and the mass of emulsifier was 6% of acrylic acid monomer.

[0034] (2) diluting the acrylic emulsion prepared in step (1) to a solid content of 2%, adding octahydroxy cage-shaped silsesquioxane monomer in an amount of 1% by weight of the acrylic emulsion, and dispersing to obtain a uniform mixture.

[0035] (3) The glass fiber is immersed in the mixture of (2) for 10 hours, taken out, and dried at 90° C. for 40 minutes to solidify and form, thereby obtaining a modified glass fiber.

[0036] Example 3 The difference from Example 2 is that the filler rope 82 is modified glass fiber.

[0037] The preparation method of the modified glass fiber is as follows: (1) Preparation of acrylic emulsion With acrylic acid as monomer, ethanol and water as dispersion medium, initiator (AIBN and K2S2O8), emulsifier (Span80 and sodium allyloxyhydroxypropane sulfonate) were used to prepare acrylic emulsion with particle size of 30-50nm. The mass of initiator was 2% of acrylic acid monomer, and the mass of emulsifier was 5% of acrylic acid monomer.

[0038] (2) diluting the acrylic emulsion prepared in step (1) to a solid content of 1%, adding 0.5% by weight of octahydroxy cage-shaped silsesquioxane monomer to the acrylic emulsion, and dispersing to obtain a uniform mixture.

[0039] (3) The glass fiber is immersed in the mixture of (2) for 6 hours, taken out, and dried at 100° C. for 20 minutes to solidify and form, thereby obtaining a modified glass fiber.

[0040] Example 4 The difference from Example 2 is that the filler rope 82 is modified glass fiber.

[0041] The preparation method of the modified glass fiber is as follows: (1) Preparation of acrylic emulsion With acrylic acid as monomer, ethanol and water as dispersion medium, initiator (AIBN and K2S2O8), emulsifier (Span80 and sodium allyloxyhydroxypropane sulfonate) were used to prepare acrylic emulsion with particle size of 30-50nm. The mass of initiator was 6% of acrylic acid monomer, and the mass of emulsifier was 8% of acrylic acid monomer.

[0042] (2) diluting the acrylic emulsion prepared in step (1) to a solid content of 3%, adding octahydroxy cage-shaped silsesquioxane monomer in an amount of 2% by weight of the acrylic emulsion, and dispersing to obtain a uniform mixture.

[0043] (3) The glass fiber is immersed in the mixture of (2) for 14 hours, taken out, and dried at 80° C. for 60 minutes to solidify and form, thereby obtaining a modified glass fiber.

[0044] Comparative Example Comparative Example 1 The difference from Example 2 is that the solid content of the acrylic emulsion is higher than the preferred range, which is 5%. The details are as follows: The preparation method of the modified glass fiber is as follows: (1) Preparation of acrylic emulsion With acrylic acid as monomer, ethanol and water as dispersion medium, initiator (AIBN and K2S2O8), emulsifier (Span80 and sodium allyloxyhydroxypropane sulfonate) were used to prepare acrylic emulsion with particle size of 30-50nm. The mass of initiator was 4% of acrylic acid monomer, and the mass of emulsifier was 6% of acrylic acid monomer.

[0045] (2) diluting the acrylic emulsion prepared in step (1) to a solid content of 5%, adding octahydroxy cage-shaped silsesquioxane monomer in an amount of 1% by weight of the acrylic emulsion, and dispersing to obtain a uniform mixture.

[0046] (3) The glass fiber is immersed in the mixture of (2) for 10 hours, taken out, and dried at 90° C. for 40 minutes to solidify and form, thereby obtaining a modified glass fiber.

[0047] Comparative Example 2 The difference from Example 2 is that no octahydroxy cage-shaped silsesquioxane monomer is added. The details are as follows: The preparation method of the modified glass fiber is as follows: (1) Preparation of acrylic emulsion With acrylic acid as monomer, ethanol and water as dispersion medium, initiator (AIBN and K2S2O8), emulsifier (Span80 and sodium allyloxyhydroxypropane sulfonate) were used to prepare acrylic emulsion with particle size of 30-50nm. The mass of initiator was 4% of acrylic acid monomer, and the mass of emulsifier was 6% of acrylic acid monomer.

[0048] (2) Dilute the acrylic emulsion prepared in step (1) to a solid content of 2%.

[0049] (3) The glass fiber is immersed in the acrylic emulsion of (2) for 10 hours, taken out, and dried at 90° C. for 40 minutes to solidify and form, thereby obtaining a modified glass fiber.

[0050] Comparative Example 3 The difference from Example 2 is that the octahydroxy cage-shaped silsesquioxane monomer is replaced by an octapolysilsesquioxane whose terminal groups are all hydrogen.

[0051] The preparation method of the modified glass fiber is as follows: (1) Preparation of acrylic emulsion With acrylic acid as monomer, ethanol and water as dispersion medium, initiator (AIBN and K2S2O8), emulsifier (Span80 and sodium allyloxyhydroxypropane sulfonate) were used to prepare acrylic emulsion with particle size of 30-50nm. The mass of initiator was 4% of acrylic acid monomer, and the mass of emulsifier was 6% of acrylic acid monomer.

[0052] (2) diluting the acrylic emulsion prepared in step (1) to a solid content of 2%, adding 1% by weight of the acrylic emulsion of octasilsesquioxane (with hydrogen at the end groups and a molecular formula of H8Si8O 12 ) and dispersed to obtain a uniform mixture.

[0053] (3) The glass fiber is immersed in the mixture of (2) for 10 hours, taken out, and dried at 90° C. for 40 minutes to solidify and form, thereby obtaining a modified glass fiber.

[0054] Comparative Example 4 The difference from Example 2 is that the amount of octahydroxy cage-shaped silsesquioxane monomer used is too much, which is 3% of the mass of the acrylic emulsion.

[0055] The preparation method of the modified glass fiber is as follows: (1) Preparation of acrylic emulsion With acrylic acid as monomer, ethanol and water as dispersion medium, initiator (AIBN and K2S2O8), emulsifier (Span80 and sodium allyloxyhydroxypropane sulfonate) were used to prepare acrylic emulsion with particle size of 30-50nm. The mass of initiator was 4% of acrylic acid monomer, and the mass of emulsifier was 6% of acrylic acid monomer.

[0056] (2) diluting the acrylic emulsion prepared in step (1) to a solid content of 2%, adding octahydroxy cage-shaped silsesquioxane monomer in an amount of 3% by weight of the acrylic emulsion, and dispersing to obtain a uniform mixture.

[0057] (3) The glass fiber is immersed in the mixture of (2) for 10 hours, taken out, and dried at 90° C. for 40 minutes to solidify and form, thereby obtaining a modified glass fiber.

[0058] Comparative Example 5 The difference from Example 2 is that the particle size of the acrylic emulsion is too small, which is 10 nm. The details are as follows: The preparation method of the modified glass fiber is as follows: (1) Preparation of acrylic emulsion With acrylic acid as monomer, ethanol and water as dispersion medium, initiator (AIBN and K2S2O8), emulsifier (Span80 and sodium allyloxyhydroxypropane sulfonate) were used to prepare acrylic emulsion with particle size of 10nm. The mass of initiator was 4% of acrylic acid monomer, and the mass of emulsifier was 10% of acrylic acid monomer.

[0059] (2) diluting the acrylic emulsion prepared in step (1) to a solid content of 2%, adding octahydroxy cage-shaped silsesquioxane monomer in an amount of 1% by weight of the acrylic emulsion, and dispersing to obtain a uniform mixture.

[0060] (3) The glass fiber is immersed in the mixture of (2) for 10 hours, taken out, and dried at 90° C. for 40 minutes to solidify and form, thereby obtaining a modified glass fiber.

[0061] Performance Testing The properties of the modified glass fibers of the embodiments and comparative examples were tested, and the results are shown in the following table.

[0062] It can be seen from the above table that compared with the commercially available filler rope in Example 1, the filler ropes made of modified glass fiber in Examples 2-4 of the present invention have a faster biofilm growth speed and a larger biofilm growth amount, which is reflected in the sewage treatment effect. With the same treatment time and process, the total nitrogen removal rate and total phosphorus removal rate of the sewage in Examples 2-4 are also higher.

[0063] The properties of the modified glass fiber are greatly affected by its preparation method. Compared with Example 2: (1) The solid content of the acrylic emulsion in Comparative Example 1 exceeds the preferred range, and the amount of film formation decreases. When the solid content is high, the viscosity of the emulsion will increase. During dipping, the emulsion is not easy to penetrate into the interior of the glass fiber. There are deep grooves on the surface of the uncoated glass fiber, and the groove distribution is relatively uniform; after dipping, the groove depth will become shallower, which is not conducive to film formation. The amount of octahydroxy cage-shaped silsesquioxane monomer used in Comparative Example 4 is too much, and the effect is reduced for the same reason. Comparative Example 5 is because the particle size is too small to block the groove, so the particle size of the emulsion should be within the preferred range.

[0064] (2) Comparative Example 2 does not add octahydroxy cage-shaped silsesquioxane monomer. On the one hand, the octahydroxy cage-shaped silsesquioxane monomer can improve the interfacial bonding force between polyacrylic acid and glass fiber, and on the other hand, it can improve the surface morphology of the fiber, increase the surface roughness of the fiber, and increase the surface energy, which is conducive to short-term film formation. Comparative Example 3 uses octahydroxy silsesquioxane whose terminal groups are all hydrogen, but the effect is not as good as octahydroxy silsesquioxane whose terminal groups are hydroxyl groups. Because acrylic acid has carboxyl groups, the hydroxyl groups of the octahydroxy cage-shaped silsesquioxane monomer can cross-link with acrylic acid to produce a network structure, promoting the above effects.

[0065] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A multi-stage AO process for removing phosphorus and nitrogen from sewage, characterized in that: Water flows through the anoxic zone 1, the anaerobic zone, the aerobic zone-anoxic zone 2 and the sedimentation zone in sequence; different zones are connected by gaps, and the gaps in adjacent zones are staggered up and down; spiral biological fillers are suspended in the anoxic zone 1 and the aerobic zone.

2. The multi-stage AO process for removing phosphorus and nitrogen from sewage according to claim 1, characterized in that: There are at least two aerobic zone-anoxic zone 2, which are arranged in series.

3. The multi-stage AO process for removing phosphorus and nitrogen from sewage according to claim 1, characterized in that: The spiral biological filler comprises a middle rope and a filler rope spirally wound on the middle rope, wherein the filler rope is a modified glass fiber, and the preparation method of the modified glass fiber is as follows: (1) adding an octahydroxy cage-shaped silsesquioxane monomer to an acrylic emulsion containing an acrylic monomer to obtain a uniform mixture; the mass of the octahydroxy cage-shaped silsesquioxane monomer is 0.5-2% of the mass of the emulsion; (2) The glass fiber is immersed in the mixture of (1), taken out, and solidified into a shape.

4. The multi-stage AO process for removing phosphorus and nitrogen from sewage according to claim 3, characterized in that: The components of the acrylic emulsion are: acrylic monomer, initiator, emulsifier, ethanol and water, and the solid content of the acrylic emulsion is 1-3%.

5. A multi-stage AO process for removing phosphorus and nitrogen from sewage according to claim 3 or 4, characterized in that: The particle size of acrylic emulsion is 30-50 nm.

6. The multi-stage AO process for removing phosphorus and nitrogen from sewage according to claim 3, characterized in that: The immersion time is 6-14 h; the curing conditions are: drying at 80-100 ℃ for 20-60 min.

7. The multi-stage AO process for removing phosphorus and nitrogen from sewage according to claim 1, characterized in that: Anaerobic activated sludge is arranged in the anaerobic zone, and facultative activated sludge is arranged in the anoxic zone 2.

8. The multi-stage AO process for removing phosphorus and nitrogen from sewage according to claim 1, characterized in that: A vertical flow tube is arranged in the center of the sedimentation area, and a hexagonal honeycomb inclined tube filler is arranged between the sedimentation area and the vertical flow tube.

9. A multi-stage AO process for removing phosphorus and nitrogen from sewage according to claim 1, 7 or 8, characterized in that: An air aeration device is provided at the bottom of the anoxic zone; an oxygen aeration device is provided at the bottom of the aerobic zone.

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