Physicochemical and biological combined system and method for advanced treatment of aircraft cleaning wastewater

Abstract

The application discloses a physicochemical-biological combined system for advanced treatment of aircraft cleaning wastewater, which comprises, sequentially and in communication along the flow direction of the wastewater, a wastewater conditioning tank, a first coagulation sedimentation tank, a physicochemical adsorption column, a photo-Fenton oxidation device, a second coagulation sedimentation tank, a simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor, a simultaneous autotrophic / heterotrophic denitrification continuous stirred tank reactor and a sludge sedimentation tank, wherein the physicochemical adsorption column is filled with magnetic hierarchical porous biomass carbon-nano-oxide composite particles, the photo-Fenton oxidation device contains FBB@COF photocatalysts, and the simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor is inoculated with hydrolysis acidification bacteria, denitrification bacteria and anaerobic ammonia oxidation bacteria; and the simultaneous autotrophic / heterotrophic denitrification continuous stirred tank reactor is inoculated with heterotrophic denitrification bacteria and autotrophic denitrification bacteria.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a physicochemical-biological combined system and method for the deep treatment of aircraft cleaning wastewater. Background Technology

[0002] Aircraft maintenance, repair, and periodic cleaning processes generate a certain amount of cleaning wastewater. This type of wastewater typically contains pollutants such as grease, surfactants, organic solvents, suspended solids, and nitrogen compounds. Among these, nitrate nitrogen is the main nitrogen pollutant, and a certain amount of ammonia nitrogen is also present.

[0003] Due to factors such as aircraft model, cleaning location, type of cleaning agent, and cleaning method, aircraft cleaning wastewater is characterized by high pollutant concentration, large fluctuations in water quality and quantity, high content of recalcitrant organic matter, and poor biodegradability. Some aircraft cleaning wastewater has a low ratio of biochemical oxygen demand (BOD) to chemical oxygen demand (COD), making it difficult to directly use conventional biological treatment processes for stable treatment.

[0004] Existing coagulation and sedimentation processes can remove suspended solids and some colloidal organic matter, but their ability to remove dissolved recalcitrant organic matter and nitrate nitrogen is limited. Conventional Fenton or photo-Fenton oxidation processes can oxidize and decompose recalcitrant organic matter, but when the influent organic load is high, it usually requires the addition of more oxidant and iron-based catalysts, and may produce more iron sludge.

[0005] When using heterotrophic denitrification alone to treat high-nitrate nitrogen wastewater, a sufficient amount of bioavailable organic carbon source is required. However, although the concentration of organic matter in aircraft cleaning wastewater is high, a large portion of it is recalcitrant and cannot be directly utilized by denitrifying bacteria. Excessive higher oxidation levels may lead to over-mineralization of the organic matter, resulting in insufficient available carbon source for subsequent denitrification.

[0006] Anaerobic ammonia oxidation (ANAO) can utilize nitrite and ammonia nitrogen for denitrification. However, aircraft cleaning wastewater typically contains nitrate nitrogen as the primary nitrogen form, and the ammonia nitrogen concentration is relatively low. Therefore, it is necessary to stably convert some nitrate nitrogen into nitrite nitrogen and match it with ammonia nitrogen. Meanwhile, in subsequent advanced denitrification stages, when organic carbon sources are insufficient, relying solely on heterotrophic denitrification is insufficient to continuously remove residual nitrate nitrogen. Summary of the Invention

[0007] The purpose of this invention is to provide a physicochemical-biological combined system and method for the deep treatment of aircraft cleaning wastewater, in order to solve problems such as easy loss of conventional adsorption materials, high cost of single advanced oxidation treatment, unreasonable matching of subsequent denitrification carbon sources, and insufficient system resistance to load shocks.

[0008] To achieve the above objectives, the present invention provides a physicochemical-biological combined system for the deep treatment of aircraft cleaning wastewater. The physicochemical-biological combined system for the deep treatment of aircraft cleaning wastewater is characterized by comprising, sequentially connected along the wastewater flow direction, a wastewater equalization tank, a first coagulation sedimentation tank, a physicochemical adsorption column, a photo-Fenton oxidation device, a second coagulation sedimentation tank, a simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor, a simultaneous autotrophic / heterotrophic denitrification continuous stirred tank reactor, and a sludge sedimentation tank.

[0009] Among them, the physicochemical adsorption column is an upflow adsorption column, which is filled with magnetic hierarchical porous biomass carbon-nano oxide composite particles (hereinafter referred to as MHPB-NO composite particles). The MHPB-NO composite particles are arranged in layers along the water flow direction of the physicochemical adsorption column according to the particle size gradient. The physicochemical adsorption column is equipped with a magnetic field component for magnetic fixation of each layer of composite particles.

[0010] The photo-Fenton oxidation unit is an upflow reactor. The reaction chamber of the upflow reactor contains FBB@COF photocatalyst and is equipped with... The FBB@COF photocatalyst is composed of FeOOH / BiOBr and a covalent organic framework COF, and includes a dosing module, a visible light irradiation module, a bottom magnetic stirring device, and an internal reflux device.

[0011] The simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor (hereinafter referred to as SFPDA-CSTR) is inoculated with hydrolytic acidifying bacteria, denitrifying bacteria and anaerobic ammonia oxidizing bacteria, so that the organic matter entering the SFPDA-CSTR after photo-Fenton oxidation treatment will be hydrolyzed and acidified to form usable organic matter. The denitrifying bacteria use the usable organic matter to convert at least part of the nitrate nitrogen into nitrite nitrogen through short-cut denitrification, and the anaerobic ammonia oxidizing bacteria use the nitrite nitrogen and ammonia nitrogen in the wastewater to carry out anaerobic ammonia oxidation reaction.

[0012] The simultaneous autotrophic / heterotrophic denitrification continuous stirred tank reactor (hereinafter referred to as SAHD-CSTR) is inoculated with heterotrophic denitrifying bacteria and autotrophic denitrifying bacteria, and filled with pyrite. It is used to carry out heterotrophic denitrification using the residual organic matter in the effluent of SFPDA-CSTR under anoxic conditions with dissolved oxygen concentration below 0.2 mg / L, and to carry out autotrophic denitrification using the inorganic electron donor provided by pyrite.

[0013] The sludge settling tank is equipped with a final outlet, a supernatant return outlet, and a sludge return outlet. The supernatant return outlet is connected to the SFPDA-CSTR through a supernatant return pipeline, and the sludge return outlet is connected to the SFPDA-CSTR through a sludge return pipeline.

[0014] In a preferred embodiment, the MHPB-NO composite particles are arranged along the upflow direction of the physicochemical adsorption column, and the particle size of the magnetic hierarchical porous biomass carbon-nano oxide composite particles increases sequentially, forming a first composite particle layer with a particle size of 10-50 μm, a second composite particle layer with a particle size of 50-100 μm, and a third composite particle layer with a particle size of 100-200 μm in sequence.

[0015] The magnetic field assembly includes multiple neodymium iron boron magnetic field units arranged along the axial direction of the physicochemical adsorption column and corresponding to the first composite particle layer, the second composite particle layer and the third composite particle layer respectively. The multiple neodymium iron boron magnetic field units can be turned on and off respectively to magnetically fix the composite particles of the corresponding particle size in sequence during the filling process of each composite particle layer.

[0016] The packing volume of MHPB-NO composite particles accounts for 70% to 80% of the effective volume of the physicochemical adsorption column.

[0017] In a preferred embodiment, the MHPB-NO composite particles comprise a hierarchical porous biomass carbon framework with micropores, mesopores, and macropores, and particles embedded in the pores of the hierarchical porous biomass carbon framework. Magnetic core-shell particles, hierarchical porous biomass carbon framework and The mass ratio of magnetic core-shell particles is 9:1; The magnetic core-shell particles have a magnetic core diameter of 25–35 nm. The coating layer is 30 nm thick.

[0018] In a preferred embodiment, the FBB@COF photocatalyst comprises a BiOBr composite FBB supported on FeOOH and a covalent organic framework COF formed by the reaction of terephthalic acid. The molar ratio of Fe to Bi in the FBB is 5:100, and the mass ratio of FBB to COF is 1:1. Multiple baffles are staggered along the water flow direction inside the upflow reactor. The angle between the multiple baffles and the horizontal plane is 45°. The vertical spacing between two adjacent baffles is 20-40 cm. A bottom magnetic stirrer is located at the bottom of the upflow reactor. An internal reflux device connects the upper outlet area and the lower inlet area of ​​the upflow reactor.

[0019] In a preferred embodiment, a polyethylene sponge packing layer is fixedly provided on the inner wall of the SFPDA-CSTR. The volume of the polyethylene sponge packing layer accounts for 20% to 30% of the effective volume of the SFPDA-CSTR. The SFPDA-CSTR is equipped with a stirring device. The polyethylene sponge packing layer is used to attach and maintain hydrolytic acidifying bacteria, denitrifying bacteria and anaerobic ammonia oxidizing bacteria.

[0020] In a preferred embodiment, the SAHD-CSTR is equipped with a stirring device and a controllable aeration device. The controllable aeration device includes an air pump, a gas flow meter, and an aeration disc located at the bottom of the SAHD-CSTR. The controllable aeration device is used to adjust the aeration rate so that the dissolved oxygen concentration in the reactor is below 0.2 mg / L. The filling volume of pyrite accounts for 10% of the effective volume of the SAHD-CSTR, and the size of a single pyrite crystal is no greater than 3 cm in each of the three mutually perpendicular directions.

[0021] In a preferred embodiment, the wastewater equalization tank is equipped with a bar screen at the inlet end, and a stirring device is provided inside the wastewater equalization tank. The first coagulation sedimentation tank and the second coagulation sedimentation tank are respectively equipped with inorganic salt coagulant dosing units. The sludge return pipeline is equipped with a sludge return pump, and the supernatant return pipeline is equipped with a supernatant return pump. The final outlet of the sludge sedimentation tank and the supernatant return outlet are respectively located at the upper part of the sludge sedimentation tank, and the sludge return outlet is located at the lower part of the sludge sedimentation tank.

[0022] This invention also provides a physicochemical-biological combined method for the deep treatment of aircraft cleaning wastewater, comprising the following steps:

[0023] S1. Adjust the water quality and quantity of aircraft cleaning wastewater;

[0024] S2. The wastewater treated in step S1 is introduced into the first coagulation sedimentation tank, and coagulant is added for the first coagulation sedimentation.

[0025] S3. The supernatant of the first coagulation sedimentation tank is passed through the physicochemical adsorption column in an upflow manner, so that the supernatant comes into contact with the magnetic graded porous biomass carbon-nano oxide composite particles arranged in layers according to the particle size gradient along the upflow direction and magnetically fixed by the magnetic field component, so as to adsorb and remove some organic matter in the wastewater and reduce the organic load entering the subsequent photo-Fenton oxidation process.

[0026] S4. Allow the effluent from the physicochemical adsorption column to enter the photo-Fenton oxidation device, where it is exposed to visible light. Photo-Fenton oxidation is carried out in conjunction with FBB@COF photocatalyst, and the contact between wastewater and FBB@COF photocatalyst is enhanced by bottom magnetic stirring, multi-stage baffles and internal reflux, so that at least some of the recalcitrant organic matter is converted into organic matter that can be utilized by the subsequent biological denitrification process.

[0027] S5. Allow the effluent from the photo-Fenton oxidation device to enter the second coagulation sedimentation tank, add coagulant for a second coagulation sedimentation, and separate the iron-containing solids generated during the photo-Fenton oxidation process.

[0028] S6. Allow the effluent from the second coagulation sedimentation tank to enter the SFPDA-CSTR, causing the organic matter to undergo hydrolysis and acidification and form usable organic matter. Denitrifying bacteria use the usable organic matter to convert at least part of the nitrate nitrogen into nitrite nitrogen through short-cut denitrification, and anaerobic ammonia oxidizing bacteria use the nitrite nitrogen and ammonia nitrogen in the wastewater to carry out anaerobic ammonia oxidation reaction.

[0029] S7. The mud-water mixture obtained in step S6 is fed into a SAHD-CSTR filled with pyrite. The residual organic matter in the mud-water mixture is used for heterotrophic denitrification, and the inorganic electron donor provided by the pyrite is used for autotrophic denitrification to further remove residual nitrate nitrogen.

[0030] S8. The mud-water mixture obtained in step S7 is fed into a sludge settling tank for mud-water separation. A portion of the supernatant obtained from the separation is discharged as the final treated effluent, and the other portion of the supernatant and at least a portion of the sludge are returned to SFPDA-CSTR.

[0031] In a preferred embodiment, the coagulant added in step S2 is an inorganic salt coagulant, and the dosage is 30-40 mg / L; the empty bed contact time of the physicochemical adsorption column in step S3 is 30-50 min.

[0032] In step S3, the magnetic hierarchical porous biomass carbon-nano oxide composite particles used are prepared by the following steps:

[0033] Will and according to and The molar ratio of the two compounds was 2:1, and the solution was dissolved in deionized water. Ammonia was added dropwise under nitrogen protection until the pH reached 11.0, and the reaction was carried out at 80°C for 6 hours to obtain the desired product. Nanoparticles;

[0034] The Nanoparticles were dispersed in a mixture of ethanol and water at a volume ratio of 3:1, and tetraethyl orthosilicate was added. The mixture was stirred for 4 h at pH 9.0 and a temperature of 50°C to obtain... Magnetic core-shell particles;

[0035] After crushing and acid washing pretreatment, sugarcane bagasse is subjected to 400℃ precarbonation, 800℃ steam activation and KOH chemical pore expansion in sequence, and then ball milling and sieving to obtain three-component graded porous biomass carbon particles with particle sizes of 10-50 μm, 50-100 μm and 100-200 μm respectively.

[0036] The fractional porous biomass carbon particles of each component are combined with the above Magnetic core-shell particles were mixed at a mass ratio of 9:1, impregnated for 30 min under vacuum pressure of -0.1 MPa and ultrasonic frequency of 40 kHz, and then vacuum dried at 60℃ for 12 h to obtain three groups of magnetic hierarchical porous biomass carbon-nano oxide composite particles with different particle sizes.

[0037] The composite particles with particle sizes of 10–50 μm, 50–100 μm, and 100–200 μm are sequentially packed along the upflow direction of the physicochemical adsorption column. When packing each group of composite particles, the neodymium iron boron magnetic field unit corresponding to the composite particle layer to be packed is turned on to magnetically fix the composite particles of the corresponding particle size.

[0038] In a preferred embodiment, the FBB@COF photocatalyst used in step S4 is prepared by the following steps:

[0039] Dissolve PEG-2000 in deionized water and add... The mixture was ultrasonically dispersed, then mixed with an aqueous KBr solution and stirred to react. After solid-liquid separation, washing, and drying, BiOBr material was obtained.

[0040] The BiOBr material was dispersed in deionized water, and Fe was added at a molar ratio of 5:100 to Bi. The aqueous solution was reacted at 50℃ for 2 h, and after solid-liquid separation, washing and drying, FeOOH-supported BiOBr complex FBB was obtained.

[0041] Terephthalic acid was added to a mixed solvent of dioxane and mesitylene and reacted at 120 °C for 24 h. After washing and drying, a covalent organic framework (COF) was obtained.

[0042] FBB was added to a 0.1 mol / L HCl solution, sonicated for 10 min, and then dispersed in ultrapure water; COF was dispersed in ultrapure water and sonicated for 10 min; the dispersed FBB and COF were mixed at a mass ratio of 1:1, N,N-dimethylformamide was added, and a solvothermal reaction was carried out at 210℃ for 2 h. After washing with ethanol and vacuum drying, the FBB@COF photocatalyst was obtained.

[0043] In step S4, the wavelength of the visible light is 420–780 nm, and the average irradiance at the surface of the reaction liquid is [missing value]. The distance between the light source and the outer wall of the photo-Fenton oxidation device is 20–30 cm; the hydraulic residence time of the photo-Fenton oxidation device is 30–60 min; the pH of the reaction solution is 3.0–4.0; the reaction temperature is 25±3℃; the bottom magnetic stirring speed is 200–300 rpm; and the concentration of the FBB@COF photocatalyst is 100–300 mg / L. The dosage concentration is 5 mmol / L, and the ratio of internal reflux water to influent water in the photo-Fenton oxidation device is 0.5:1 to 0.6:1;

[0044] The amount of inorganic salt coagulant added in step S5 is less than the amount of inorganic salt coagulant added in step S2.

[0045] In step S6, the inoculation volume ratio of hydrolytic acidifying bacteria, denitrifying bacteria, and anaerobic ammonia oxidizing bacteria in the simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor is 4:4:1. The inoculated sludge volume accounts for 40% to 50% of the effective volume of the reactor. The total suspended solids concentration of the initial mixed liquor is 6500 to 8000 mg / L, the ratio of volatile suspended solids concentration to total suspended solids concentration is 0.4 to 0.7, the hydraulic retention time is 12 to 16 h, the operating pH is 7 to 8, the reaction temperature is 30±2℃, the stirring speed is 50 to 80 rpm, the dissolved oxygen concentration is controlled at 0.1 to 0.3 mg / L and not higher than 0.5 mg / L, and the oxidation-reduction potential is controlled at -100 to -50 mV.

[0046] In step S7, the inoculation volume ratio of heterotrophic denitrifying bacteria to autotrophic denitrifying bacteria in the simultaneous autotrophic / heterotrophic denitrification continuous stirred tank reactor is 3:1. The inoculated sludge volume accounts for 40% to 50% of the effective volume of the reactor. The total suspended solids concentration of the initial mixed liquor is 3500 to 4000 mg / L, the ratio of volatile suspended solids concentration to total suspended solids concentration is 0.4 to 0.7, the operating pH is 7 to 8, the reaction temperature is 30±2℃, the hydraulic retention time is 4 to 8 h, and the aeration rate is adjusted by a controllable aeration device to keep the dissolved oxygen concentration below 0.2 mg / L.

[0047] In step S8, the ratio of sludge return flow rate to influent flow rate in step S6 is 1:1 to 1:3.

[0048] Compared with the prior art, the beneficial effects of the present invention are:

[0049] 1. This invention forms a continuous treatment chain through first coagulation sedimentation, magnetic graded adsorption, visible light Fenton oxidation, second coagulation sedimentation, and two-stage biological denitrification, capable of treating suspended solids, colloidal organic matter, recalcitrant organic matter, and nitrogen-containing pollutants respectively. MHPB-NO composite particles are stratified according to a particle size gradient and fixed by corresponding magnetic field units, reducing the risk of fine adsorption particles being lost with the upflow and improving particle distribution and flow conditions within the adsorption column. The physicochemical adsorption column first reduces part of the organic load, and the photo-Fenton oxidation device then oxidizes and transforms the remaining recalcitrant organic matter, avoiding reliance solely on the photo-Fenton process to handle the entire organic matter removal load. FBB@COF photocatalyst, visible light, Baffles, magnetic stirring, and internal reflux work together to improve the reaction contact within the photo-Fenton oxidation unit. The second coagulation sedimentation tank can further remove iron-containing solids, reducing their impact on subsequent biological treatment.

[0050] 2. The SFPDA-CSTR of this invention couples hydrolysis acidification, short-cut denitrification, and anaerobic ammonium oxidation processes, enabling the usable organic matter formed by hydrolysis acidification to be used for short-cut denitrification, while simultaneously utilizing the nitrite nitrogen and ammonia nitrogen produced by short-cut denitrification for anaerobic ammonium oxidation. The SAHD-CSTR can utilize residual organic matter for heterotrophic denitrification, and when usable organic matter is insufficient, it can utilize inorganic electron donors provided by pyrite for autotrophic denitrification, thereby improving the system's adaptability to carbon source fluctuations.

[0051] 3. The supernatant and sludge of the sludge sedimentation tank of the present invention are respectively returned to SFPDA-CSTR, which is beneficial to re-treat the residual nitrogen in the return liquid and maintain the number of functional bacteria in the reactor. Attached Figure Description

[0052] Figure 1 This is a structural diagram of the physicochemical-biological combined system for deep treatment of aircraft cleaning wastewater according to the present invention.

[0053] Figure 2 This is a schematic diagram of the physicochemical adsorption column structure of the present invention;

[0054] Figure 3 This is a schematic diagram of the structure of the photo-Fenton oxidation device of the present invention;

[0055] Figure 4 This is a schematic diagram of the SFPDA-CSTR structure of the present invention;

[0056] Figure 5 This is a schematic diagram of the SAHD-CSTR structure of the present invention.

[0057] Explanation of reference numerals in the attached figures:

[0058] 1-Wastewater equalization tank; 2-First coagulation sedimentation tank; 3-Physicochemical adsorption column; 4-Photo-Fenton oxidation device; 5-Second coagulation sedimentation tank; 6-SFPDA-CSTR; 7-SAHD-CSTR; 8-Sludge sedimentation tank; 21-Physicochemical adsorption column inlet pump; 22-Physicochemical adsorption column body; 23-MHPB-NO composite particles of different sizes; 24-NdFeB magnetic field unit; 31-Photo-Fenton oxidation device inlet; 32-Upflow reactor; 33-Visible light irradiation module; 34-Baffle plate; 35- Storage bucket; 36- 37-Inlet pump; 38-FBB@COF photocatalyst; 39-Bottom magnetic stirrer; 40-Internal reflux pump; 41-Outlet of photo-Fenton oxidation unit; 42-SFPDA-CSTR inlet; 43-SFPDA-CSTR reactor body; 44-SFPDA-CSTR stirring equipment; 45-Polyethylene sponge packing layer; 46-Sludge reflux pump; 47-Supernatant reflux pump; 51-SAHD-CSTR inlet; 52-SAHD-CSTR reactor body; 53-SAHD-CSTR stirring equipment; 54-Pyrite; 55-Gas flow meter; 56-Air pump; 57-Aeration disc; 58-SAHD-CSTR outlet. Detailed Implementation

[0059] The technical solutions in the embodiments of the present invention will be clearly and completely described below. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention.

[0060] like Figure 1 As shown, the physicochemical-biological combined system for deep treatment of aircraft cleaning wastewater in this embodiment includes a wastewater equalization tank 1, a first coagulation sedimentation tank 2, a physicochemical adsorption column 3, a photo-Fenton oxidation device 4, a second coagulation sedimentation tank 5, a simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor 6, a simultaneous autotrophic / heterotrophic denitrification continuous stirred tank reactor 7, and a sludge sedimentation tank 8.

[0061] Wastewater equalization tank 1 is equipped with a screen at its inlet and a stirring device inside. The screen is used to trap larger debris in the wastewater, and the stirring device is used to mix aircraft cleaning wastewater from different sources or batches to balance the water quality and quantity. A first coagulation sedimentation tank 2 is connected to the outlet of wastewater equalization tank 1. The first coagulation sedimentation tank 2 is equipped with an inorganic salt coagulant dosing unit for adding inorganic salt coagulants to the equalized wastewater to remove suspended solids, colloidal substances, and some organic matter. A physicochemical adsorption column 3 is connected to the supernatant outlet of the first coagulation sedimentation tank 2. The physicochemical adsorption column 3 is an upflow adsorption column filled with MHPB-NO composite particles. The MHPB-NO composite particles are arranged in layers according to a particle size gradient along the water flow direction of the physicochemical adsorption column. The physicochemical adsorption column 3 is equipped with a magnetic field component for magnetically fixing each layer of composite particles. The photo-Fenton oxidation device 4 is an upflow reactor. The reaction chamber of the upflow reactor contains FBB@COF photocatalyst and is equipped with... The reactor includes a dosing module, a visible light irradiation module, a bottom magnetic stirring device, and an internal reflux device. The FBB@COF photocatalyst is formed by the composite of FeOOH / BiOBr and covalent organic framework COF. Multiple baffles are staggered along the water flow direction within the upflow reactor. The photo-Fenton oxidation device 4 is used to oxidize and transform at least a portion of the recalcitrant organic matter in the effluent from the physicochemical adsorption column, reducing the organic load of the wastewater to facilitate subsequent hydrolysis, acidification, and biological denitrification. The second coagulation sedimentation tank 5 is located between the photo-Fenton oxidation device 4 and the SFPDA-CSTR, used to remove iron-containing solids from the wastewater treated by photo-Fenton oxidation.

[0062] Along the upflow direction of the physicochemical adsorption column, the MHPB-NO composite particles exhibit a progressively increasing particle size, forming a first composite particle layer with a particle size of 10–50 μm, a second composite particle layer with a particle size of 50–100 μm, and a third composite particle layer with a particle size of 100–200 μm. The magnetic field assembly includes multiple NdFeB magnetic field units arranged axially along the physicochemical adsorption column and corresponding to the first, second, and third composite particle layers, respectively. These NdFeB magnetic field units can be individually activated and deactivated to magnetically fix the composite particles of corresponding sizes during the filling process of each composite particle layer. The filling volume of the MHPB-NO composite particles occupies 70%–80% of the effective volume of the physicochemical adsorption column. The MHPB-NO composite particles comprise a hierarchical porous biomass carbon framework with micropores, mesopores, and macropores, and particles embedded within the pores of this hierarchical porous biomass carbon framework. Magnetic core-shell particles, hierarchical porous biomass carbon framework and The mass ratio of magnetic core-shell particles is 9:1; The magnetic core-shell particles have a magnetic core diameter of 25–35 nm. The coating thickness is 30 nm. The magnetic response intensity of the magnetic core-shell particles is 35±2 emu / g.

[0063] The preparation process of MHPB-NO composite particles is as follows: and according to and Dissolved in deionized water at a molar ratio of 2:1, ammonia was added dropwise under nitrogen protection until the pH reached 11.0, and the mixture was reacted at 80°C for 6 h to obtain... Nanoparticles were dispersed in a mixture of ethanol and water (volume ratio 3:1), and tetraethyl orthosilicate was added. The mixture was stirred at pH 9.0 and 50°C for 4 hours to obtain... Magnetic core-shell particles; sugarcane bagasse is crushed, acid-washed, and then subjected to pre-carbonization at 400℃, steam activation at 800℃, and KOH chemical pore expansion, followed by ball milling and sieving to obtain three-component fractionated porous biomass carbon particles of 10–50 μm, 50–100 μm, and 100–200 μm; each group of carbon particles is compared with... The MHPB-NO composite particles were mixed at a mass ratio of 9:1, vacuum impregnated for 30 min under a negative pressure of 0.1 MPa and ultrasonication at 40 kHz, and then vacuum dried at 60℃ for 12 h to obtain three groups of MHPB-NO composite particles.

[0064] Furthermore, the photo-Fenton oxidation device uses visible light at 420–780 nm, with an average irradiance of 120–150 mW / cm² at the reaction liquid surface, and a distance of 20–30 cm between the light source and the outer wall of the reactor. The hydraulic residence time of the photo-Fenton oxidation device is 30–60 min, the pH of the reaction liquid is 3.0–4.0, the reaction temperature is 25±3℃, and the bottom magnetic stirring speed is 200–300 rpm. A metering pump is used for continuous flow feeding, so that the contents of the reactor are fed continuously. The steady-state concentration was maintained at 5 mmol / L, with an allowable fluctuation of ±0.3 mmol / L.

[0065] The FBB@COF photocatalyst comprises a BiOBr complex FBB supported on FeOOH and a covalent organic framework COF formed by the reaction of terephthalic acid. The molar ratio of Fe to Bi in the FBB is 5:100, and the mass ratio of FBB to COF is 1:1. The multi-stage baffles are at an angle of 45° to the horizontal plane, and the vertical spacing between adjacent baffles is 20–40 cm. The bottom magnetic stirrer is located at the bottom of the upflow reactor, and the internal reflux device connects the upper effluent area and the lower influent area of ​​the upflow reactor.

[0066] The preparation process of the FBB@COF photocatalyst is as follows: PEG-2000 is dissolved in deionized water, and then... The mixture was ultrasonically dispersed, then mixed with KBr aqueous solution for reaction. After solid-liquid separation, washing, and drying, BiOBr was obtained. Fe was added at a molar ratio of 5:100 to Bi. FBB was obtained by reacting an aqueous solution at 50°C for 2 h; COF was obtained by reacting terephthalic acid in a mixed solvent of dioxane and mesitylene at 120°C for 24 h; FBB and COF were ultrasonically dispersed separately and then mixed at a mass ratio of 1:1, N,N-dimethylformamide was added, and the mixture was solvothermal reacted at 210°C for 2 h. FBB@COF was obtained by washing with ethanol and vacuum drying.

[0067] The SFPDA-CSTR is inoculated with hydrolytic acidifying bacteria, denitrifying bacteria, and anaerobic ammonia oxidizing bacteria. The hydrolytic acidifying bacteria are used to further hydrolyze and acidify the organic matter entering the SFPDA-CSTR after photo-Fenton oxidation treatment and form usable organic matter. The denitrifying bacteria use the usable organic matter as an electron donor to convert at least part of the nitrate nitrogen into nitrite nitrogen through short-cut denitrification. The anaerobic ammonia oxidizing bacteria use the nitrite nitrogen and ammonia nitrogen in the wastewater to carry out an anaerobic ammonia oxidation reaction.

[0068] The SAHD-CSTR is inoculated with heterotrophic and autotrophic denitrifying bacteria and filled with pyrite. This allows for heterotrophic denitrification using residual organic matter in the SFPDA-CSTR effluent and autotrophic denitrification using pyrite as an inorganic electron donor.

[0069] Furthermore, the SFPDA-CSTR was started up using a phased, incremental load method, while the SAHD-CSTR was started up using simultaneous inoculation and a gradual increase in load. The start-up period for both bioreactors was 35–45 days. After reaching the design operating load, operation continued, and the system was considered to have reached a stable operating state when the relative standard deviations of COD, nitrate nitrogen, and ammonia nitrogen concentrations in the effluent were all less than 5% for seven consecutive days. The reaction temperature during the biological treatment stage was controlled at 30±2℃; the hydraulic retention time of the SFPDA-CSTR was 12–16 h, the stirring speed was 50–80 rpm, the dissolved oxygen concentration was controlled at 0.1–0.3 mg / L and not exceeding 0.5 mg / L, and the oxidation-reduction potential was controlled at [missing information]. The hydraulic retention time of SAHD-CSTR is 4–8 h, and the dissolved oxygen concentration is controlled below 0.2 mg / L.

[0070] The sludge sedimentation tank 8 is equipped with a final outlet, a supernatant return outlet, and a sludge return outlet. The supernatant return outlet is connected to the SFPDA-CSTR through a supernatant return pipeline, and the sludge return outlet is connected to the SFPDA-CSTR through a sludge return pipeline.

[0071] The SFPDA-CSTR has a polyethylene sponge packing layer fixedly installed on its inner wall, with the volume of the polyethylene sponge packing layer accounting for 20% to 30% of the effective volume of the SFPDA-CSTR. The SFPDA-CSTR is equipped with a stirring device. The polyethylene sponge packing layer is used to attach and maintain hydrolytic acidifying bacteria, denitrifying bacteria, and anaerobic ammonia-oxidizing bacteria. The SAHD-CSTR is equipped with a stirring device and a controllable aeration device, which includes an air pump, a gas flow meter, and an aeration disc located at the bottom of the SAHD-CSTR. This device is used to adjust the aeration rate to keep the dissolved oxygen concentration in the SAHD-CSTR below 0.2 mg / L. The pyrite filling volume accounts for 10% of the effective volume of the SAHD-CSTR, and the size of a single pyrite particle in any of the three mutually perpendicular directions is no greater than 3 cm.

[0072] In a preferred embodiment, the pyrite is natural pyrite, and its main component is... , The mass fraction is not less than 90%. The natural pyrite, after crushing and screening, selects particles with triaxial dimensions not exceeding 3 cm, soaks them in 1 mol / L dilute hydrochloric acid for 4 h, rinses them with deionized water until neutral, and then dries them at 105℃ for 12 h. During stable system operation, the sulfate concentration in the SAHD-CSTR effluent increases by approximately 30–50 mg / L compared to its influent, the total iron concentration is 0.15–0.30 mg / L, of which the ferrous iron concentration is 0.05–0.15 mg / L.

[0073] The first and second coagulation sedimentation tanks are each equipped with an inorganic salt coagulant dosing unit. The sludge return pipeline is equipped with a sludge return pump, and the supernatant return pipeline is equipped with a supernatant return pump. The final outlet of the sludge sedimentation tank and the supernatant return outlet are respectively located at the upper part of the sludge sedimentation tank, and the sludge return outlet is located at the lower part of the sludge sedimentation tank.

[0074] The sources and start-up of inoculated sludge included: hydrolytic acidifying bacteria from anaerobic sludge from a pharmaceutical wastewater hydrolysis acidification reactor; denitrifying bacteria from sludge from anoxic denitrification reactors that had been treating nitrate wastewater for a long time and then enriched and acclimated to nitrite nitrogen; anaerobic ammonia oxidizing bacteria from granular sludge from an anaerobic ammonia oxidizing reactor that had been enriched in the laboratory for a long time; and heterotrophic and autotrophic denitrifying bacteria from activated sludge from anoxic tanks of municipal wastewater treatment plants, which were then directionally enriched and passaged 3-5 times in a pyrite-containing medium. The SFPDA-CSTR was started up at 30%, 60%, 80%, and 100% of the design flow rate in four incremental stages, each stage lasting 7 days; the SAHD-CSTR was started up at 50% of the design flow rate for 7 days and then gradually increased to 100%.

[0075] The total nitrogen removal rate of the SFPDA-CSTR unit mentioned in this manual is calculated using the measured TN of the effluent from the second coagulation sedimentation tank (external main water flow) as the influent total nitrogen concentration, and the measured TN of the SFPDA-CSTR effluent as the effluent total nitrogen concentration. The total nitrogen removal rate of the entire system is calculated using the measured TN of the equalization tank effluent (total system influent) and the final net effluent from the sludge sedimentation tank. The actual TN of the mixed influent to the SFPDA-CSTR... , , Organic nitrogen is also included in the reflux nitrogen load verification data and is not used as the denominator of the total nitrogen removal rate of the above units.

[0076] Example 1:

[0077] In this embodiment, the physicochemical adsorption column is filled with MHPB-NO composite particles arranged in layers according to a particle size gradient. The filling volume of the MHPB-NO composite particles accounts for 80% of the effective volume of the physicochemical adsorption column. Along the upflow direction of the physicochemical adsorption column, a first composite particle layer with a particle size of 10-50 μm, a second composite particle layer with a particle size of 50-100 μm, and a third composite particle layer with a particle size of 100-200 μm are arranged sequentially from bottom to top. Each composite particle layer is magnetically fixed by a corresponding NdFeB magnetic field unit. The angle between the baffles in the photo-Fenton oxidation device and the horizontal plane is 45°, and the vertical spacing between adjacent baffles is 25 cm. The concentration of the FBB@COF photocatalyst is 150 mg / L. The dosage concentration was 5 mmol / L, and the ratio of internal return water to influent was 0.5:1. The volume of the polyethylene sponge packing layer in the SFPDA-CSTR occupied 20% of the reactor's effective volume. The inoculation volume ratio of hydrolytic acidifying bacteria, denitrifying bacteria, and anaerobic ammonia oxidizing bacteria was 4:4:1, and the inoculated sludge volume occupied 40% of the reactor's effective volume. The initial mixed liquor total suspended solids concentration was 6500 mg / L, the ratio of volatile suspended solids concentration to total suspended solids concentration was 0.5, and the operating pH was 7.5. The pyrite packing volume occupied 10% of the SAHD-CSTR's effective volume, and the size of a single pyrite particle in any of the three mutually perpendicular directions was no greater than 3 cm. The dissolved oxygen concentration in the SAHD-CSTR was controlled below 0.2 mg / L using a controlled aeration device.

[0078] The above system is used to treat aircraft cleaning wastewater, including the following steps:

[0079] S1, Adjustment process.

[0080] Aircraft cleaning wastewater is filtered through a screen installed at the inlet of the wastewater equalization tank before entering the equalization tank. There, it is thoroughly mixed by a stirring device to balance the water quality and quantity. After equalization, the wastewater... The concentration is 400 mg / L. The concentration was 10 mg / L, and the COD concentration was 2500 mg / L.

[0081] S2, First coagulation and sedimentation.

[0082] The effluent from the wastewater equalization tank was introduced into the first coagulation sedimentation tank, where 30 mg / L polyaluminum chloride was added for coagulation and sedimentation. After the first coagulation and sedimentation, approximately 90% of the suspended solids in the wastewater were removed, and the COD concentration of the supernatant from the first coagulation sedimentation tank was 2370 mg / L, a reduction of 130 mg / L.

[0083] S3, magnetic hierarchical physicochemical adsorption.

[0084] The supernatant from the first coagulation sedimentation tank is introduced into the physicochemical adsorption column via an upflow, and then sequentially passes through the first, second, and third composite particle layers. The empty bed contact time of the physicochemical adsorption column is 30 min. Organic matter in the wastewater is adsorbed by the MHPB-NO composite particles, and the COD concentration of the treated effluent is 1945 mg / L. The COD concentration difference between the influent and effluent in step S3 is 425 mg / L, accounting for 17% of the COD concentration of the influent to the wastewater equalization tank.

[0085] S4, visible light Fenton oxidation.

[0086] The effluent from the physicochemical adsorption column was fed into the photo-Fenton oxidation unit, where 150 mg / L of FBB@COF photocatalyst and 5 mmol / L of [unspecified ingredient] were added. The visible light irradiation module, bottom magnetic stirring device, and internal reflux device are activated. The ratio of internal reflux water volume to influent water volume is 0.5:1. Under conditions of upflow, multi-stage baffles, magnetic stirring, and internal reflux, the wastewater reacts with the FBB@COF photocatalyst and Sufficient contact is ensured to induce the oxidative transformation of recalcitrant organic matter. The photo-Fenton HRT was set at 45 min, pH 3.5 ± 0.2, temperature 25 ± 3℃, and stirring at 250 rpm. The COD concentration of the effluent from the photo-Fenton oxidation unit was 815 mg / L. The COD concentration difference between the influent and effluent in step S4 was 1130 mg / L, accounting for 45.2% of the COD concentration of the influent to the wastewater equalization tank.

[0087] S5, Secondary coagulation and sedimentation.

[0088] The effluent from the photo-Fenton oxidation unit enters the second coagulation sedimentation tank, where 20 mg / L of polyaluminum chloride is added to remove iron-containing solids and other suspended matter generated during the photo-Fenton oxidation process. The COD concentration of the supernatant from the second coagulation sedimentation tank is 755 mg / L.

[0089] S6. Simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation treatment. The supernatant from the second coagulation sedimentation tank enters the SFPDA-CSTR. Hydrolysis acidification bacteria convert some of the large-molecule organic matter in the wastewater into organic matter that can be utilized by denitrification bacteria; denitrification bacteria use this organic matter as an electron donor to convert nitrate nitrogen into nitrite nitrogen via short-cut denitrification; anaerobic ammonia oxidation bacteria utilize nitrite nitrogen and ammonia nitrogen for anaerobic ammonia oxidation. The hydraulic retention time of the SFPDA-CSTR is 12 h. The ratio of the supernatant return flow rate from the sludge sedimentation tank to the SFPDA-CSTR influent flow rate is 1.5:1, stirring is performed at 50–80 rpm, DO = 0.1–0.3 mg / L, and ORP = -100–-50 mV.

[0090] S7, Simultaneous autotrophic / heterotrophic denitrification treatment.

[0091] The effluent from the SFPDA-CSTR was then introduced into the SAHD-CSTR. In the SAHD-CSTR, heterotrophic denitrifying bacteria utilized the residual organic matter in the SFPDA-CSTR effluent for heterotrophic denitrification, while autotrophic denitrifying bacteria utilized inorganic electron donors provided by pyrite for autotrophic denitrification. The SAHD-CSTR had a hRT of 6 h and DO < 0.2 mg / L. After treatment with the SAHD-CSTR, the effluent COD concentration was 23 mg / L.

[0092] S8, mud-water separation and reflux.

[0093] The effluent from the SAHD-CSTR enters a sludge settling tank for sludge-water separation. A portion of the supernatant obtained from the sludge settling tank is discharged through the final effluent outlet, while the remaining supernatant is returned to the SFPDA-CSTR via a supernatant return pipeline. Similarly, the settled sludge is returned to the SFPDA-CSTR via a sludge return pipeline. The ratio of sludge return flow rate to SFPDA-CSTR influent flow rate is 1:1.5.

[0094] The effluent water quality of each treatment unit in Example 1 is as follows:

[0095]

[0096] We can obtain the following results: Total nitrogen removal rate of SFPDA-CSTR unit = (413-36.5) / 413×100% = 91.2%; Total nitrogen removal rate of the whole system = (416-0.95) / 416×100% = 99.77%; COD removal rate of the system = (2500-23) / 2500×100% = 99.08%.

[0097] Example 2:

[0098] This embodiment uses the same system as Embodiment 1, with the following differences:

[0099] The MHPB-NO composite particles filled 75% of the effective volume of the physicochemical adsorption column. The vertical spacing between adjacent baffles in the photo-Fenton oxidation device was 30 cm. The FBB@COF photocatalyst was added at a concentration of 200 mg / L. The dosage concentration was 5 mmol / L, and the ratio of internal return water to influent was 0.6:1. The volume of the polyethylene sponge packing layer in the SFPDA-CSTR occupied 25% of the reactor's effective volume. The inoculation volume ratio of hydrolytic acidifying bacteria, denitrifying bacteria, and anaerobic ammonia-oxidizing bacteria was 4:4:1. The inoculated sludge volume occupied 45% of the reactor's effective volume, the initial mixed liquor total suspended solids concentration was 7000 mg / L, the volatile suspended solids concentration to total suspended solids concentration ratio was 0.6, and the operating pH was 7.0. In the SAHD-CSTR, the inoculation volume ratio of heterotrophic denitrifying bacteria and autotrophic denitrifying bacteria was 3:1. The inoculated sludge volume in the SAHD-CSTR occupied 40% of the reactor's effective volume, the initial mixed liquor total suspended solids concentration was 3500 mg / L, the volatile suspended solids concentration to total suspended solids concentration ratio was 0.5, the operating pH was 7.5, and the dissolved oxygen concentration was controlled below 0.2 mg / L.

[0100] The above system is used to treat aircraft cleaning wastewater, including the following steps:

[0101] S1, Adjustment process.

[0102] Aircraft cleaning wastewater is filtered through a screen before entering a wastewater equalization tank, where its quality and quantity are balanced by stirring. After equalization, the wastewater... The concentration is 450 mg / L. The concentration was 15 mg / L, and the COD concentration was 2800 mg / L.

[0103] S2, First coagulation and sedimentation.

[0104] The effluent from the wastewater equalization tank was introduced into the first coagulation sedimentation tank, where 37 mg / L of polyaluminum chloride was added for coagulation and sedimentation. After treatment, the COD concentration of the supernatant from the first coagulation sedimentation tank was 2647 mg / L, a reduction of 153 mg / L.

[0105] S3, magnetic hierarchical physicochemical adsorption.

[0106] The supernatant from the first coagulation sedimentation tank was passed through the physicochemical adsorption column in an upflow manner, with an empty bed contact time of 40 min. After treatment, the COD concentration of the effluent from the physicochemical adsorption column was 2115 mg / L. The COD concentration difference between the influent and effluent in step S3 was 532 mg / L, accounting for 19% of the COD concentration of the influent to the wastewater equalization tank.

[0107] S4, visible light Fenton oxidation.

[0108] The effluent from the physicochemical adsorption column was fed into the photo-Fenton oxidation unit, with 200 mg / L of FBB@COF photocatalyst and 5 mmol / L of H2O2 added. The visible light irradiation module, bottom magnetic stirrer, and internal reflux device were turned on, and the ratio of internal reflux water to influent was controlled at 0.6:1. The photo-Fenton HRT was 40 min, pH 3.5 ± 0.2, temperature 25 ± 3 ℃, and stirring was 200–300 rpm. After treatment, the COD concentration of the effluent from the photo-Fenton oxidation unit was 820 mg / L. The COD concentration difference between the influent and effluent in step S4 was 1295 mg / L, accounting for 46.25% of the COD concentration of the influent in the wastewater equalization tank.

[0109] S5, Secondary coagulation and sedimentation.

[0110] The effluent from the photo-Fenton oxidation unit was fed into the second coagulation sedimentation tank, where 20 mg / L of polyaluminum chloride was added to remove iron-containing solids and other suspended matter. After treatment, the COD concentration of the supernatant in the second coagulation sedimentation tank was 807 mg / L.

[0111] S6, simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonium oxidation treatment.

[0112] The supernatant from the second coagulation sedimentation tank was fed into the SFPDA-CSTR. The hydraulic retention time of the SFPDA-CSTR was 14 h, the supernatant reflux ratio was 1.2:1, the stirring speed was 50–80 rpm, the DO concentration was 0.1–0.3 mg / L, and the ORP was -100–-50 mV. After treatment, the COD concentration of the effluent from the SFPDA-CSTR was 103 mg / L.

[0113] S7, Simultaneous autotrophic / heterotrophic denitrification treatment.

[0114] The effluent from the SFPDA-CSTR was introduced into the SAHD-CSTR, where heterotrophic denitrification was performed using residual organic matter, and autotrophic denitrification was performed using inorganic electron donors provided by pyrite. The dissolved oxygen concentration in the SAHD-CSTR was controlled below 0.2 mg / L using a controlled aeration device. After treatment, the COD concentration of the SAHD-CSTR effluent was 29 mg / L, the nitrate nitrogen concentration was 0.6 mg / L, and the ammonia nitrogen concentration was 0.1 mg / L.

[0115] S8, mud-water separation and reflux.

[0116] The effluent from the SAHD-CSTR enters a sludge settling tank for sludge-water separation. A portion of the supernatant is discharged as final treated effluent, while the remaining supernatant and at least a portion of the settled sludge are returned to the SFPDA-CSTR. The ratio of sludge return flow rate to SFPDA-CSTR influent flow rate is 1:1.2.

[0117] The effluent water quality of each treatment unit in Example 2 is as follows:

[0118]

[0119] We can obtain the following results: Total nitrogen removal rate of SFPDA-CSTR unit = (469-34.5) / 469×100% = 92.6%; Total nitrogen removal rate of the whole system = (472-0.80) / 472×100% = 99.83%; COD removal rate of the system is approximately 98.96%.

[0120] Example 3:

[0121] This embodiment uses the same system and material preparation method as Example 1 to illustrate the operation under conditions of higher adsorbent material filling volume, with the following differences:

[0122] The MHPB-NO composite particles filled 75% of the effective volume of the physicochemical adsorption column. The vertical spacing between adjacent baffles in the photo-Fenton oxidation device was 40 cm. The FBB@COF photocatalyst was added at a concentration of 300 mg / L. The dosage concentration was 5 mmol / L, and the ratio of internal return water to influent was 0.5:1. In the SFPDA-CSTR, the volume of the polyethylene sponge packing layer occupied 30% of the reactor's effective volume. The inoculation volume ratio of hydrolytic acidifying bacteria, denitrifying bacteria, and anaerobic ammonia-oxidizing bacteria was 4:4:1. The inoculated sludge volume occupied 40% of the reactor's effective volume. The initial mixed liquor total suspended solids concentration was 6500 mg / L, the volatile suspended solids concentration to total suspended solids concentration ratio was 0.6, and the operating pH was 8.0. In the SAHD-CSTR, the inoculation volume ratio of heterotrophic denitrifying bacteria and autotrophic denitrifying bacteria was 3:1. The inoculated sludge volume in the SAHD-CSTR occupied 45% of the reactor's effective volume. The initial mixed liquor total suspended solids concentration was 4000 mg / L, the volatile suspended solids concentration to total suspended solids concentration ratio was 0.6, and the operating pH was 8.0.

[0123] The above system is used to treat aircraft cleaning wastewater, including the following steps.

[0124] S1, Adjustment process.

[0125] Aircraft cleaning wastewater is filtered through a screen before entering a wastewater equalization tank, where its quality and quantity are balanced by stirring. After equalization, the wastewater... The concentration is 500 mg / L. The concentration was 20 mg / L, and the COD concentration was 3000 mg / L.

[0126] S2, First coagulation and sedimentation.

[0127] The effluent from the wastewater equalization tank was introduced into the first coagulation sedimentation tank, where 40 mg / L of polyaluminum chloride was added for coagulation and sedimentation. After treatment, the COD concentration of the supernatant from the first coagulation sedimentation tank was 2833 mg / L, a reduction of 167 mg / L.

[0128] S3, magnetic hierarchical physicochemical adsorption.

[0129] The supernatant from the first coagulation sedimentation tank is passed through the physicochemical adsorption column in an upflow manner, with an empty bed contact time of 50 min. After treatment, the COD concentration of the effluent from the physicochemical adsorption column is 2293 mg / L. The COD concentration difference between the influent and effluent in step S3 is 540 mg / L, accounting for 18% of the COD concentration of the influent to the wastewater equalization tank.

[0130] S4, visible light Fenton oxidation.

[0131] The effluent from the physicochemical adsorption column is fed into the photo-Fenton oxidation unit, where 300 mg / L of FBB@COF photocatalyst and 5 mmol / L of [unspecified ingredient] are added. Turn on the visible light irradiation module, bottom magnetic stirrer, and internal reflux device, controlling the ratio of internal reflux water to influent to 0.5:1. Set the photo-Fenton HRT to 50 min, pH to 3.5±0.2, temperature to 25±3 ℃, and stirring speed to 200–300 rpm. After treatment, the COD concentration of the effluent from the photo-Fenton oxidation unit is 928 mg / L. The COD concentration difference between the influent and effluent in step S4 is 1365 mg / L, accounting for 45.5% of the COD concentration of the influent to the wastewater equalization tank.

[0132] S5, Secondary coagulation and sedimentation.

[0133] The effluent from the photo-Fenton oxidation unit was fed into the second coagulation sedimentation tank, where 20 mg / L of polyaluminum chloride was added to remove iron-containing solids and other suspended matter. After treatment, the COD concentration of the supernatant in the second coagulation sedimentation tank was 915 mg / L.

[0134] S6, simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonium oxidation treatment.

[0135] The supernatant from the second coagulation sedimentation tank is introduced into the SFPDA-CSTR. The hydraulic retention time of the SFPDA-CSTR is 16 h, the ratio of supernatant return flow rate to SFPDA-CSTR influent flow rate is 1.7:1, stirring is performed at 50-80 rpm, DO = 0.1-0.3 mg / L, and ORP = -100--50 mV.

[0136] S7, Simultaneous autotrophic / heterotrophic denitrification treatment.

[0137] The effluent from the SFPDA-CSTR enters the SAHD-CSTR, where heterotrophic denitrification is performed using residual organic matter, and autotrophic denitrification is performed using inorganic electron donors provided by pyrite. The dissolved oxygen concentration in the SAHD-CSTR is controlled below 0.2 mg / L using a controlled aeration device. After treatment, the COD concentration of the SAHD-CSTR effluent is 25 mg / L.

[0138] S8, mud-water separation and reflux.

[0139] The effluent from the SAHD-CSTR enters a sludge settling tank for sludge-water separation. A portion of the supernatant is discharged as final treated effluent, while the remaining supernatant and at least a portion of the settled sludge are returned to the SFPDA-CSTR. The ratio of sludge return flow rate to SFPDA-CSTR influent flow rate is 1:1.7.

[0140] The effluent water quality of each treatment unit in Example 3 is as follows:

[0141]

[0142] We can obtain the following results: Total nitrogen removal rate of SFPDA-CSTR unit = (526-45.5) / 526×100% = 91.3%; Total nitrogen removal rate of the whole system = (529-2.1) / 529×100% = 99.60%; COD removal rate of the system is approximately 99.17%.

[0143] Example 4:

[0144] To verify the simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonium oxidation reaction pathway within the SFPDA-CSTR, sludge and corresponding influent from the SFPDA-CSTR during the stable operation phase of Example 1 were used to conduct a 12-hour offline batch test in an independent closed batch reactor, following the temperature, pH, stirring, and DO / ORP conditions of Example 1. During the test, there was no continuous influent and no supernatant recirculation, and the nitrogen speciation was monitored sequentially according to the table below.

[0145]

[0146] Nitrite nitrogen exhibits a dynamic change of "accumulation first—reaching a peak—and then consumption," supporting short-range denitrification. The reaction pathway is then consumed by subsequent anaerobic ammonia oxidation and simultaneous denitrification.

[0147]

[0148] From day 30 onwards, the total nitrate (TN) in the SFPDA-CSTR effluent stabilized within the range of approximately 38–42 mg / L. Long-term levels below 3 mg / L.

[0149] Nitrogen mass balance calculation was performed based on the measured nitrogen concentration at 0 h of the offline batch test:

[0150]

[0151] Anaerobic ammonia oxidation, heterotrophic denitrification, and assimilation synthesis are used to explain the different fates of TN removal; this calculation is used to help explain that SFPDA-CSTR is not a single denitrification unit.

[0152] On day 45 of stable operation, the functional microbial community and activity of the SFPDA-CSTR sludge were tested, and the results are as follows:

[0153]

[0154] The aforementioned data on nitrogen speciation, functional gene abundance, and sludge activity collectively support the coupled operation of the three functional bacterial communities within the SFPDA-CSTR.

[0155] Example 5:

[0156] This example provides single-factor and stratified combination controlled trials:

[0157] All control experiments used Example 1 as the baseline, with influent COD = 2500 mg / L. =400 mg / L =10 mg / L, with 3 parallel reactors set up in each group, and continuous operation for 30 days. The following data are expressed as mean ± standard deviation. The statistical stable operation period is from day 25 to 30.

[0158] (1) Contribution of gradient stratification and magnetic field fixation in physicochemical adsorption columns:

[0159]

[0160] Layered packing and magnetic field fixation both improved the adsorption removal rate and operational stability. Among them, the combination of layered packing and magnetic field fixation resulted in the lowest effluent SS, the lowest column pressure drop, and the highest adsorption capacity retention rate after 30 days.

[0161] (2) Contribution of FBB@COF chemical complexation:

[0162]

[0163] Compared to the physical mixing of FBB / COF, the FBB@COF chemical composite further improves the removal rate of COD and TOC, reaction rate and cycle stability, and reduces Fe leaching.

[0164] (3) Contribution of the SFPDA-CSTR tribacterial combination:

[0165]

[0166] Where D represents denitrifying bacteria, H represents hydrolytic acidifying bacteria, and A represents anaerobic ammonia oxidizing bacteria. The combination of these three bacteria showed the highest TN removal rate and SAA removal rate.

[0167] (4) Contribution of SAHD-CSTR autotrophic / heterotrophic combination:

[0168]

[0169] The combination of heterotrophic denitrification under anoxic conditions and pyrite-mediated autotrophic denitrification can achieve both residual organic matter removal and deep denitrification.

[0170] (5) The combined contribution of sludge recirculation and supernatant recirculation:

[0171]

[0172] The dual reflux system simultaneously maintains the biomass of functional microorganisms and the alkalinity / substrate balance of the reactor, enabling the system to operate stably for more than 60 days.

[0173] Comparative Example 1:

[0174] This comparative example was conducted concurrently with Example 1, using essentially the same processing flow and operating conditions as Example 1. The differences were as follows: the MHPB-NO composite particles in the physicochemical adsorption column were not graded according to particle size, but were instead packed with medium-sized composite particles; the photocatalyst added to the photo-Fenton oxidation device was FBB prepared according to the above-mentioned FBB preparation steps, and was not combined with COF; the SFPDA-CSTR was inoculated only with mature denitrifying bacteria and anaerobic ammonia oxidizing bacteria at a volume ratio of 4:1, and no hydrolytic acidifying bacteria were inoculated; the SAHD-CSTR was not inoculated with pyrite, and was only inoculated with mature heterotrophic denitrifying bacteria.

[0175] Other operating conditions are the same as in Example 1.

[0176] The effluent quality of each treatment unit in Comparative Example 1 is as follows:

[0177]

[0178] The test results show that the total COD removal rate of Comparative Example 1 was 89.24%, and the total nitrogen removal rate was approximately 91.71%. Compared with Example 1, Comparative Example 1 did not use MHPB-NO composite particles with particle size gradient stratification, FBB@COF photocatalyst, or pyrite-mediated autotrophic denitrification process, and its final COD concentration and nitrate nitrogen concentration were significantly higher than those of Example 1.

[0179] Comparative Example 2:

[0180] This comparative example was conducted concurrently with Example 2, using essentially the same processing flow and operating conditions as Example 2. The differences were as follows: the MHPB-NO composite particles in the physicochemical adsorption column were not stratified according to particle size, and all were filled with large-diameter particles; the photocatalyst added to the photo-Fenton oxidation device was FBB prepared according to the above-mentioned FBB preparation steps, and was not combined with COF; SFPDA-CSTR and SAHD-CSTR were inoculated only with mature denitrifying bacteria, and were not configured according to the functional bacterial community combination defined in this invention; the subsequent bioreactor did not use a combination of heterotrophic denitrification and pyrite-mediated autotrophic denitrification.

[0181] Other operating conditions are the same as in Example 2.

[0182] The effluent quality of each treatment unit in Comparative Example 2 is as follows:

[0183]

[0184] The total COD removal rate of Comparative Example 2 was approximately 99.11%, and the total nitrogen removal rate was approximately 86.02%. Although Comparative Example 2 reduced COD, the final TN was still approximately 65 mg / L, significantly higher than the 0.80 mg / L in Example 2, indicating that removing only organic matter does not guarantee deep removal of total nitrogen. The hydrolytic acidification, short-cut denitrification, and anaerobic ammonia-oxidizing bacteria in the SFPDA-CSTR, and the heterotrophic denitrification, autotrophic denitrification bacteria, and pyrite in the SAHD-CSTR, as per this invention, are beneficial for improving the deep nitrogen removal effect of the system.

[0185] In summary, in Examples 1-3, the apparent total nitrogen removal rates of SFPDA-CSTR, calculated based on the external main water flow concentration, were 91.2%, 92.6%, and 91.3%, respectively, while the actual measured total nitrogen removal rates for the entire system were 99.77%, 99.83%, and 99.60%, respectively. Single-factor comparisons further showed that particle size gradient stratification and magnetic field fixation, chemical combination of FBB and COF, three-bacterial combination, autotrophic / heterotrophic denitrification combination, and dual reflux all contributed to the system performance and long-term stability.

[0186] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A physicochemical-biological combined system for the deep treatment of aircraft cleaning wastewater, characterized in that: It includes a wastewater equalization tank, a first coagulation sedimentation tank, a physicochemical adsorption column, a photo-Fenton oxidation device, a second coagulation sedimentation tank, a simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor, a simultaneous autotrophic / heterotrophic denitrification continuous stirred tank reactor, and a sludge sedimentation tank, all connected sequentially along the wastewater flow direction. The physicochemical adsorption column is an upflow adsorption column, and the physicochemical adsorption column is filled with magnetic hierarchical porous biomass carbon-nano oxide composite particles. The magnetic hierarchical porous biomass carbon-nano oxide composite particles are arranged in layers along the water flow direction of the physicochemical adsorption column according to the particle size gradient. The physicochemical adsorption column is equipped with a magnetic field component for magnetically fixing each layer of composite particles. The photo-Fenton oxidation device is an upflow reactor, and the reaction chamber of the upflow reactor contains an FBB@COF photocatalyst and is equipped with... The FBB@COF photocatalyst is composed of FeOOH / BiOBr and a covalent organic framework COF, and includes a dosing module, a visible light irradiation module, a bottom magnetic stirring device, and an internal reflux device. The second coagulation sedimentation tank is located between the photo-Fenton oxidation device and the simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor, and is used to remove iron-containing solids from the wastewater after photo-Fenton oxidation treatment; The simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor is inoculated with hydrolysis acidifying bacteria, denitrifying bacteria and anaerobic ammonia oxidation bacteria, so that the organic matter entering the reactor after the photo-Fenton oxidation treatment will be hydrolyzed and acidified to form usable organic matter. The denitrifying bacteria use the usable organic matter to convert at least part of the nitrate nitrogen into nitrite nitrogen through short-cut denitrification, and the anaerobic ammonia oxidation bacteria use the nitrite nitrogen and ammonia nitrogen in the wastewater to carry out anaerobic ammonia oxidation reaction. The simultaneous autotrophic / heterotrophic denitrification continuous stirred tank reactor is inoculated with heterotrophic and autotrophic denitrifying bacteria and filled with pyrite. It is used to perform heterotrophic denitrification using the residual organic matter in the effluent of the simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor under anoxic conditions with dissolved oxygen concentration below 0.2 mg / L, and to perform autotrophic denitrification using the inorganic electron donor provided by the pyrite. The sludge sedimentation tank is equipped with a final outlet, a supernatant return outlet, and a sludge return outlet. The supernatant return outlet is connected to the simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonium oxidation continuous stirred tank reactor via a supernatant return pipeline. The sludge return outlet is connected to the simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonium oxidation continuous stirred tank reactor via a sludge return pipeline.

2. The physicochemical-biological combined system for deep treatment of aircraft cleaning wastewater according to claim 1, characterized in that: Along the upflow direction of the physicochemical adsorption column, the particle size of the magnetic hierarchical porous biomass carbon-nano oxide composite particles increases sequentially, and a first composite particle layer with a particle size of 10-50 μm, a second composite particle layer with a particle size of 50-100 μm, and a third composite particle layer with a particle size of 100-200 μm are formed sequentially. The magnetic field assembly includes multiple neodymium iron boron magnetic field units arranged along the axial direction of the physicochemical adsorption column and corresponding to the first composite particle layer, the second composite particle layer and the third composite particle layer respectively. The multiple neodymium iron boron magnetic field units can be turned on and off respectively to magnetically fix the composite particles of the corresponding particle size in sequence during the filling process of each composite particle layer. The filling volume of the magnetic hierarchical porous biomass carbon-nano oxide composite particles accounts for 70% to 80% of the effective volume of the physicochemical adsorption column.

3. The physicochemical-biological combined system for deep treatment of aircraft cleaning wastewater according to claim 1, characterized in that: The magnetic hierarchical porous biomass carbon-nano oxide composite particles include a hierarchical porous biomass carbon framework with micropores, mesopores, and macropores, and particles embedded in the pores of the hierarchical porous biomass carbon framework. Magnetic core-shell particles, the hierarchical porous biomass carbon framework and the The mass ratio of magnetic core-shell particles is 9:1; The magnetic core-shell particles have a magnetic core diameter of 25–35 nm. The coating layer is 30 nm thick.

4. The physicochemical-biological combined system for deep treatment of aircraft cleaning wastewater according to claim 1, characterized in that: The FBB@COF photocatalyst comprises a BiOBr complex FBB supported on FeOOH and a covalent organic framework COF formed by the reaction of terephthalic acid. The molar ratio of Fe to Bi in the FBB is 5:100, and the mass ratio of FBB to COF is 1:

1. Multiple stages of baffles are staggered along the water flow direction inside the upflow reactor. The angle between the multiple stages of baffles and the horizontal plane is 45°, and the vertical spacing between adjacent stages of baffles is 20–40 cm. The bottom magnetic stirring device is located at the bottom of the upflow reactor, and the internal reflux device connects the upper outlet area and the lower inlet area of ​​the upflow reactor.

5. The physicochemical-biological combined system for deep treatment of aircraft cleaning wastewater according to claim 1, characterized in that: The inner wall of the simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor is fixedly provided with a polyethylene sponge packing layer. The volume of the polyethylene sponge packing layer accounts for 20% to 30% of the effective volume of the simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor. The simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor is equipped with a stirring device. The polyethylene sponge packing layer is used to attach and maintain the hydrolysis acidification bacteria, denitrification bacteria and anaerobic ammonia oxidation bacteria.

6. The physicochemical-biological combined system for deep treatment of aircraft cleaning wastewater according to claim 1, characterized in that: The simultaneous autotrophic / heterotrophic denitrification continuous stirred tank reactor is equipped with a stirring device and a controllable aeration device. The controllable aeration device includes an air pump, a gas flow meter, and an aeration disc located at the bottom of the simultaneous autotrophic / heterotrophic denitrification continuous stirred tank reactor. The controllable aeration device is used to adjust the aeration rate so that the dissolved oxygen concentration in the reactor is below 0.2 mg / L. The filling volume of the pyrite accounts for 10% of the effective volume of the simultaneous autotrophic / heterotrophic denitrification continuous stirred tank reactor, and the size of a single pyrite crystal in three mutually perpendicular directions is no greater than 3 cm.

7. The physicochemical-biological combined system for deep treatment of aircraft cleaning wastewater according to claim 1, characterized in that: The wastewater equalization tank is equipped with a screen at its inlet end and a stirring device inside. The first coagulation sedimentation tank and the second coagulation sedimentation tank are each equipped with an inorganic salt coagulant dosing unit. The sludge return pipeline is equipped with a sludge return pump, and the supernatant return pipeline is equipped with a supernatant return pump. The final outlet and supernatant return outlet of the sludge sedimentation tank are respectively located at the upper part of the sludge sedimentation tank, and the sludge return outlet is located at the lower part of the sludge sedimentation tank.

8. A physicochemical-biological combined method for the deep treatment of aircraft cleaning wastewater, characterized in that, Includes the following steps: S1. Adjust the water quality and quantity of aircraft cleaning wastewater; S2. The wastewater treated in step S1 is introduced into the first coagulation sedimentation tank, and coagulant is added for the first coagulation sedimentation. S3. The supernatant of the first coagulation sedimentation tank is passed through the physicochemical adsorption column in an upflow manner, so that the supernatant comes into contact with the magnetic graded porous biomass carbon-nano oxide composite particles arranged in layers according to the particle size gradient along the upflow direction and magnetically fixed by the magnetic field component, so as to adsorb and remove some organic matter in the wastewater and reduce the organic load entering the subsequent photo-Fenton oxidation process. S4. Allow the effluent from the physicochemical adsorption column to enter the photo-Fenton oxidation device, where it is exposed to visible light. Photo-Fenton oxidation is carried out in conjunction with FBB@COF photocatalyst, and the contact between wastewater and FBB@COF photocatalyst is enhanced by bottom magnetic stirring, multi-stage baffles and internal reflux, so that at least some of the recalcitrant organic matter is converted into organic matter that can be utilized by the subsequent biological denitrification process. S5. Allow the effluent from the photo-Fenton oxidation device to enter the second coagulation sedimentation tank, add coagulant for a second coagulation sedimentation, and separate the iron-containing solids generated during the photo-Fenton oxidation process. S6. The effluent from the second coagulation sedimentation tank is fed into a simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor, where organic matter is hydrolyzed and acidified to form usable organic matter. Denitrifying bacteria use the usable organic matter to convert at least part of nitrate nitrogen into nitrite nitrogen via short-cut denitrification, and anaerobic ammonia oxidation bacteria use the nitrite nitrogen and ammonia nitrogen in the wastewater to carry out an anaerobic ammonia oxidation reaction. S7. The mud-water mixture obtained in step S6 is fed into a simultaneous autotrophic / heterotrophic denitrification continuous stirred tank reactor filled with pyrite. Under anoxic conditions with dissolved oxygen concentration below 0.2 mg / L, heterotrophic denitrification is carried out using the residual organic matter in the mud-water mixture, and autotrophic denitrification is carried out using the inorganic electron donor provided by the pyrite, so as to further remove residual nitrate nitrogen. S8. The mud-water mixture obtained in step S7 is fed into a sludge sedimentation tank for mud-water separation. A portion of the supernatant obtained from the separation is discharged as the final treated effluent, and the other portion of the supernatant and at least a portion of the sludge are returned to the simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor.

9. The physicochemical-biological combined method for deep treatment of aircraft cleaning wastewater according to claim 8, characterized in that, The coagulant added in step S2 is an inorganic salt coagulant, and the dosage is 30-40 mg / L; the empty bed contact time of the physicochemical adsorption column in step S3 is 30-50 min; In step S3, the magnetic hierarchical porous biomass carbon-nano oxide composite particles used are prepared by the following steps: Will and according to and The molar ratio of the two compounds was 2:1, and the solution was dissolved in deionized water. Ammonia was added dropwise under nitrogen protection until the pH reached 11.0, and the reaction was carried out at 80°C for 6 hours to obtain the desired product. Nanoparticles; The Nanoparticles were dispersed in a mixture of ethanol and water at a volume ratio of 3:1, and tetraethyl orthosilicate was added. The mixture was stirred for 4 h at pH 9.0 and a temperature of 50°C to obtain... Magnetic core-shell particles; After crushing and acid washing pretreatment, sugarcane bagasse is subjected to 400℃ precarbonation, 800℃ steam activation and KOH chemical pore expansion in sequence, and then ball milling and sieving to obtain three-component graded porous biomass carbon particles with particle sizes of 10-50 μm, 50-100 μm and 100-200 μm respectively. The fractional porous biomass carbon particles of each component are combined with the above Magnetic core-shell particles were mixed at a mass ratio of 9:1, impregnated for 30 min under vacuum pressure of -0.1 MPa and ultrasonic frequency of 40 kHz, and then vacuum dried at 60℃ for 12 h to obtain three groups of magnetic hierarchical porous biomass carbon-nano oxide composite particles with different particle sizes. The composite particles with particle sizes of 10–50 μm, 50–100 μm, and 100–200 μm are sequentially packed along the upflow direction of the physicochemical adsorption column. When packing each group of composite particles, the neodymium iron boron magnetic field unit corresponding to the composite particle layer to be packed is turned on to magnetically fix the composite particles of the corresponding particle size.

10. The physicochemical-biological combined method for deep treatment of aircraft cleaning wastewater according to claim 8 or 9, characterized in that, In step S4, the FBB@COF photocatalyst used is prepared by the following steps: Dissolve PEG-2000 in deionized water and add... The mixture was ultrasonically dispersed, then mixed with an aqueous KBr solution and stirred to react. After solid-liquid separation, washing, and drying, BiOBr material was obtained. The BiOBr material was dispersed in deionized water, and Fe was added at a molar ratio of 5:100 to Bi. The aqueous solution was reacted at 50℃ for 2 h, and after solid-liquid separation, washing and drying, FeOOH-supported BiOBr complex FBB was obtained. Terephthalic acid was added to a mixed solvent of dioxane and mesitylene and reacted at 120 °C for 24 h. After washing and drying, a covalent organic framework (COF) was obtained. FBB was added to a 0.1 mol / L HCl solution, sonicated for 10 min, and then dispersed in ultrapure water; COF was dispersed in ultrapure water and sonicated for 10 min; the dispersed FBB and COF were mixed at a mass ratio of 1:1, N,N-dimethylformamide was added, and a solvothermal reaction was carried out at 210℃ for 2 h. After washing with ethanol and vacuum drying, the FBB@COF photocatalyst was obtained. In step S4, the wavelength of the visible light is 420–780 nm, the average irradiance at the surface of the reaction liquid is 120–150 mW / cm², the distance between the light source and the outer wall of the photo-Fenton oxidation device is 20–30 cm, the hydraulic residence time of the photo-Fenton oxidation device is 30–60 min, the pH of the reaction liquid is 3.0–4.0, the reaction temperature is 25±3℃, the bottom magnetic stirring speed is 200–300 rpm, and the concentration of the FBB@COF photocatalyst is 100–300 mg / L. The dosage concentration is 5 mmol / L, and the ratio of the internal reflux water volume to the influent water volume of the photo-Fenton oxidation device is 0.5:1 to 0.6:1; The amount of inorganic salt coagulant added in step S5 is less than the amount of inorganic salt coagulant added in step S2. In step S6, the inoculation volume ratio of hydrolytic acidifying bacteria, denitrifying bacteria, and anaerobic ammonia oxidizing bacteria in the simultaneous hydrolysis acidification-short-cut denitrification-anaerobic ammonia oxidation continuous stirred tank reactor is 4:4:

1. The inoculated sludge volume accounts for 40% to 50% of the effective volume of the reactor. The total suspended solids concentration of the initial mixed liquor is 6500 to 8000 mg / L, the ratio of volatile suspended solids concentration to total suspended solids concentration is 0.4 to 0.7, the hydraulic retention time is 12 to 16 h, the operating pH is 7 to 8, the reaction temperature is 30±2℃, the stirring speed is 50 to 80 rpm, the dissolved oxygen concentration is controlled at 0.1 to 0.3 mg / L and not higher than 0.5 mg / L, and the oxidation-reduction potential is controlled at -100 to -50 mV. In step S7, the inoculation volume ratio of heterotrophic denitrifying bacteria to autotrophic denitrifying bacteria in the simultaneous autotrophic / heterotrophic denitrification continuous stirred tank reactor is 3:

1. The inoculated sludge volume accounts for 40% to 50% of the effective volume of the reactor. The total suspended solids concentration of the initial mixed liquor is 3500 to 4000 mg / L, the ratio of volatile suspended solids concentration to total suspended solids concentration is 0.4 to 0.7, the operating pH is 7 to 8, the reaction temperature is 30±2℃, the hydraulic retention time is 4 to 8 h, and the aeration rate is adjusted by a controllable aeration device to keep the dissolved oxygen concentration below 0.2 mg / L. In step S8, the ratio of sludge return flow rate to influent flow rate in step S6 is 1:1 to 1:3.

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