A nitrogen and phosphorus wastewater treatment system and method

Abstract

This invention provides a nitrogen and phosphorus wastewater treatment system and method. The system includes a pre-anoxic tank, an inclined plate sedimentation tank, an anaerobic tank, an anoxic tank, a homogenization reaction tank, a synergistic oxidation tank, and a storage tank. The storage tank is connected to the homogenization reaction tank via a material transport pipeline, and the homogenization reaction tank is equipped with a stirring group. The storage tank contains a carbon-based composite material with a surface loaded with manganese oxides and magnesium oxides. The carbon-based composite material is added to the homogenization reaction tank through the material transport pipeline, and stirring ensures uniform mixing of the material and the mixed liquid, achieving homogenization and adhesion, and enhancing the subsequent synergistic oxidation effect. The carbon-based composite material provides a reaction interface for microorganisms, organic matter, and sludge, increasing microbial diversity and enabling synergistic oxidation with microorganisms to improve the degradation efficiency of nitrogen and phosphorus pollutants. This invention has a simple structure, does not require continuous aerobic aeration, and has advantages such as small footprint, short hydraulic retention time, low operating energy consumption, continuous influent and effluent, and high nitrogen and phosphorus pollutant removal efficiency.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a nitrogen-phosphorus organic wastewater treatment system and method. Background Technology

[0002] With the rapid development of industrialization and urbanization and the continuous improvement of social living standards, the discharge of urban sewage is constantly increasing. The effluent from sewage treatment plants contains persistent organic pollutants, endocrine disruptors, antibiotics and other pollutants. After long-term accumulation in the aquatic environment, these pollutants not only cause eutrophication of surface water bodies, but also pose extremely high ecological risks.

[0003] Currently, wastewater treatment plants commonly employ traditional biological treatment processes such as AAO, oxidation ditches, SBR, and their modified forms. These processes suffer from drawbacks including large footprints, high energy consumption, difficulty in achieving simultaneous and efficient biological nitrogen and phosphorus removal, and poor treatment efficacy for new pollutants. Therefore, innovation in traditional biological wastewater treatment processes is urgently needed. To reduce footprint, lower energy consumption, decrease carbon emissions, and improve simultaneous nitrogen and phosphorus removal efficiency and the removal rate of new pollutants, combining biological and physicochemical treatment methods (such as membrane filtration, ion exchange, and adsorption) is an important direction for improving and innovating wastewater treatment processes. Summary of the Invention

[0004] To address the problems of traditional biological treatment processes, such as large footprint, high energy consumption, difficulty in achieving simultaneous and efficient biological nitrogen and phosphorus removal, and poor treatment effect on new pollutants, this invention aims to provide a nitrogen and phosphorus wastewater treatment system and method. A carbon-based composite material with surface-loaded manganese and magnesium oxides is added to the activated sludge in a homogenization reaction tank, and stirring is used to achieve homogenization and adhesion. The carbon-based composite material has a high specific surface area and a variable-valence metal interface, enabling efficient adsorption of pollutants and microorganisms on the surface. A large number of free radicals with high redox potentials are generated at the interface. Through the synergistic effects of microorganisms, physical, chemical, and catalytic oxidation, efficient and deep removal of nitrogen and phosphorus pollutants from wastewater is achieved. This overcomes the shortcomings of traditional biological treatment processes, such as long hydraulic retention time, continuous aerobic aeration, difficulty in achieving simultaneous and efficient biological nitrogen and phosphorus removal, and poor treatment effect on new pollutants. Fundamentally, this invention provides a novel, intensive, low-carbon, and efficient wastewater treatment system and method based on a carbon-based composite material with variable-valence metal oxides coupled with an activated sludge biological treatment process.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A nitrogen-phosphorus wastewater treatment system includes a pre-anoxic tank, an inclined plate sedimentation tank, an anaerobic tank, an anoxic tank, and an outlet. It also includes a homogenization reaction tank, a co-oxidation tank, a material transport pipeline, and a storage tank. The inlet of the nitrogen-phosphorus wastewater treatment system is connected to the anaerobic tank, and the anaerobic tank, anoxic tank, homogenization reaction tank, and co-oxidation tank are sequentially connected. The inclined plate sedimentation tank has a sludge discharge outlet and a supernatant discharge outlet; the sludge discharge outlet is connected to the pre-anoxic tank, and the supernatant discharge outlet is connected to the co-oxidation tank. Each of the pre-anoxic tank, anaerobic tank, and anoxic tank is equipped with a stirring device. The pre-anoxic tank is connected to the anaerobic tank via a pipeline. The outlet of the storage tank is connected to the material transport pipeline, and the material transport pipeline is connected to the homogenization reaction tank. The homogenization reaction tank contains several stirring groups. The co-oxidation tank has a mixed liquor return channel, a sludge return channel, and several aeration devices. The mixed liquor return channel is connected to the anoxic tank, the sludge return channel is connected to the inclined plate sedimentation tank, and the outlet of the co-oxidation tank is connected to the outlet.

[0007] The present invention includes a storage tank for adding carbon-based composite materials. The storage tank delivers materials to a homogenization reaction tank through a material transport pipeline. A stirring device in the homogenization reaction tank stirs and mixes the mixture from the anoxic tank and the materials from the storage tank to homogenize the reaction interface and provide conditions for subsequent aeration oxidation in the synergistic oxidation tank.

[0008] Furthermore, the number of the synergistic oxidation tanks is two; the two synergistic oxidation tanks alternately receive water and operate intermittently to achieve continuous operation of the sewage treatment system.

[0009] Furthermore, the nitrogen and phosphorus wastewater treatment system also includes a return tank and a separation tank. The synergistic oxidation tank has a bottom tank containing a sludge pump. The outlet of the sludge pump is connected to the separation tank. The separation tank contains a backwash water pump and a magnetic field device that can be turned on or off. The discharge port of the separation tank is connected to one end of a material return pipeline, and the other end of the material return pipeline is connected to the return tank. The outlet of the return tank is connected to the material transport pipeline. This facilitates the reuse of magnetic carbon-based composite materials and saves on treatment costs.

[0010] Furthermore, the magnetic field device includes a magnetic induction coil disposed in the separation cell and a switching device for controlling the energization and de-energization of the magnetic induction coil.

[0011] Furthermore, a diaphragm metering pump is installed at the outlet of the reflux tank and the storage tank, and the outlet of the diaphragm metering pump is connected to the material transport pipeline.

[0012] Furthermore, the slope of the bottom surface of the synergistic oxidation tank is 5~10°.

[0013] The bottom surface of the co-oxidation tank has a slope, which facilitates the deposition of sludge in the bottom tank and makes it easy to discharge. Optionally, the magnetic carbon-based composite material is a carbon-based composite material loaded with magnetic materials. This invention also provides a nitrogen and phosphorus wastewater treatment method, employing the nitrogen and phosphorus wastewater treatment system described above; sludge from the pre-anoxic tank is discharged into the anaerobic tank through a pipeline; wastewater with a pH of 6-9 enters the anaerobic tank through the inlet; the wastewater and sludge in the anaerobic tank are mixed for phosphorus release reaction and then discharged into the anoxic tank for denitrification reaction; the mixed liquid in the anoxic tank is discharged into the homogenization reaction tank; an appropriate amount of carbon-based composite material from the storage tank is added into the homogenization reaction tank through a material transport pipeline; the stirring group is started to ensure that the carbon-based composite material and the mixed liquid are mixed evenly under stirring to obtain a homogenized mixed liquid; the homogenized mixed liquid is discharged into the co-oxidation tank. In the oxidation tank, the aeration device is turned on for aeration oxidation treatment. During the aeration process, part of the mixed liquor is returned to the anoxic tank through the mixed liquor return channel. After the aeration reaction is completed, the aeration device is turned off, and the mixed liquor is separated by sedimentation to obtain treated liquid and sludge. The treated liquid is discharged through the outlet for further treatment, and part of the sludge is returned to the inclined plate sedimentation tank through the sludge return channel. Part of the sludge is discharged outside the nitrogen and phosphorus wastewater treatment system. After sedimentation, the sludge in the inclined plate sedimentation tank is concentrated sludge and supernatant from the inclined plate. The concentrated sludge is discharged into the pre-anoxic tank through the sludge discharge outlet, and the supernatant from the inclined plate is discharged into the co-oxidation tank through the supernatant discharge outlet.

[0014] The carbon-based composite material uses biochar as a carrier, with manganese oxides and magnesium oxides loaded on the surface of the biochar. Simultaneously, the carbon-based composite material is added to the homogenization reaction tank, and a stirring device is activated to obtain a homogenized mixture. This allows microorganisms, sludge, and organic matter in the mixture to adhere uniformly to the carbon-based composite material, serving a pre-adsorption function and concentrating reactants at the interface of the material or sludge particles, thus enhancing the aerobic effect of the subsequent synergistic oxidation tank. The homogenized mixture is then discharged into the synergistic oxidation tank, and aeration is activated. Aeration agitates the mixture and increases dissolved oxygen in the water. At this point, vigorous aerobic microbial reactions occur at the interface of the carbon-based composite material or suspended sludge particles. Furthermore, the carbon-based composite material self-excites and generates free radicals to oxidize pollutants in the wastewater, achieving COD degradation, ammonia nitrogen nitrification, phosphorus over-absorption, and phosphorus magnesification. Phosphorus is then transferred to the sludge through biological phosphorus uptake and the phosphorus magnesification product, magnesium ammonium phosphate.

[0015] Furthermore, based on the COD in the wastewater cr The content of NH3-N, TP and BOD5 / COD cr The ratio adjustment is the amount of carbon-based composite material added per cubic meter of wastewater, A0, where A0 = baseline value A1 + additional value A2;

[0016] The criteria for adding the baseline value A1 are as follows:

[0017] CODcr ≤100mg / L, A1=2kg / m 3 100mg / L < COD cr ≤200mg / L, A1=4kg / m 3 200mg / L < COD cr ≤300mg / L, A1=6kg / m 3 COD cr >300mg / L, A1=2*COD cr / 100;

[0018] The additional value A2 ≥ 0, preferably 0~4 kg / m 3 ;

[0019] The criteria for adding the additional value A2 are as follows:

[0020] (1) When BOD5 / COD cr When A2 > 0.58 and / or TP < 12 mg / L, A2 = 0;

[0021] (2) When BOD5 / COD cr When the concentration of TP is 0.45~0.58, and / or when the concentration of TP is 12~15 mg / L, A2 = 0.5 kg / m 3 ;

[0022] (3) When BOD5 / COD cr When the concentration of TP is 0.30~0.45, and / or when the concentration of TP is 15~19 mg / L, A2 = 1 kg / m 3 ;

[0023] (4) When BOD5 / COD cr <0.3, and / or, when TP is >19 mg / m³, A2 ≥4 kg / m³ 3 Preferably 4 kg / m 3 .

[0024] Furthermore, the specific surface area of ​​the carbon-based composite material is not less than 180 m². 2 / g, optionally, the mass ratio of biochar to manganese oxide and magnesium oxide is 1:0.6~0.95:0.95~1.6, preferably 1:0.7~0.85:1~1.5.

[0025] In some embodiments of the present invention, the carbon-based composite material is prepared by the following steps: 60-80 mesh dried plant-derived biomass is mixed with divalent manganese salt and permanganate in an aqueous solution at a ratio of 200-500 g: 1.5-2.5 mol: 1-1.5 mol (preferably 300-400 g: 1.8-2.3 mol: 1.1-1.4 mol). The mixed solution is washed, filtered, and freeze-dried to obtain manganese-loaded biomass. The manganese-loaded biomass is mixed with inorganic magnesium salt at a mass ratio of 1:1-1.6 (preferably 1:1.1-1.4) and ground to obtain sample powder. The sample powder is pyrolyzed at 650-750°C for 2-3 hours under an argon atmosphere to obtain manganese and magnesium bimetallic biochar, i.e., the carbon-based composite material.

[0026] Optionally, the inorganic magnesium salt is one or more of magnesium chloride, magnesium nitrate, and magnesium sulfate.

[0027] The carbon-based composite material has a multi-layered structure, retaining the high specific surface area and porous interface characteristics of biochar, while also being doped with abundant metals and functional groups. It can directly generate free radicals, exhibiting high oxidation performance. These free radicals can directly oxidize nitrogen and phosphorus organic compounds, or first oxidize manganese to obtain high-valence manganese, further oxidizing nitrogen and phosphorus organic compounds. They can also activate oxidants, enhancing their degradation efficiency for nitrogen and phosphorus organic compounds. Simultaneously, the surface-loaded magnesium has a high adsorption capacity and selectivity for phosphates, enhancing the limited heavy metal stabilization capacity of biochar.

[0028] In the process of wastewater treatment, organic matter needs to be metabolized into inorganic matter by microorganisms. The degradation of organic matter requires sufficient carbon source to support microbial metabolism. Appropriate carbon source supplementation can overcome problems such as the imbalance of carbon-nitrogen ratio and carbon-phosphorus ratio during metabolism, low BOD / COD ratio, and low efficiency of simultaneous biological nitrogen and phosphorus removal.

[0029] Furthermore, when the wastewater BOD5 / TN value is ≤3.5 and / or the water temperature is less than 12℃, a carbon source is added.

[0030] Furthermore, the carbon source is at least one of glucose, sodium acetate, methanol, and ethanol.

[0031] Furthermore, the amount of carbon source added is 0.01~0.05 kg / m³. 3 .

[0032] Optionally, the aeration flow rate is 10-20 m³ / min, preferably 12-18 m³ / min.

[0033] Furthermore, the nitrogen and phosphorus wastewater treatment system also includes a return tank and a separation tank; the synergistic oxidation tank is equipped with a bottom tank, the bottom tank is equipped with a sludge pump, the outlet of the sludge pump is connected to the separation tank, the separation tank is equipped with a backwash water pump and a magnetic field device that can be turned on or off, the discharge port of the separation tank is connected to one end of the material return pipeline, the other end of the material return pipeline is connected to the return tank, and the outlet of the return tank is connected to the material transport pipeline;

[0034] Part of the sludge from the co-oxidation tank is fed into the separation tank. The magnetic field device is turned on, causing the carbon-based composite material to adhere to the magnetic field device, resulting in residual sludge. After the residual sludge is completely discharged outside the separation tank, the magnetic field device is turned off, and the backwash water pump is turned on to rinse the attached carbon-based composite material, causing it to accumulate in the separation tank, thus obtaining a carbon-based composite material slurry. The carbon-based composite material slurry is then transported to the return tank through the material return pipeline.

[0035] Optionally, sodium periodate is added to the synergistic oxidation tank so that the concentration of sodium periodate in the mixed system in the synergistic oxidation tank is 1-3 mmol / L, preferably 1.5-2.5 mmol / L.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) A new wastewater treatment system and method based on carbon-based composite material with variable valence metal oxide loading coupled with activated sludge biological treatment process is provided. It can be integrated in the form of one tank and multiple units, without the need for continuous aerobic aeration. It has significant advantages such as small footprint, short hydraulic retention time, low operating energy consumption, continuous influent and effluent, and high removal efficiency of nitrogen and phosphorus pollutants.

[0038] (2) Based on the activated sludge biological treatment process, a homogenization reaction tank with a stirring group is set up, which can stir and mix the mixed liquid from the anoxic tank and the carbon-based composite material from the storage tank evenly. This not only homogenizes the reaction interface and provides conditions for subsequent aeration and synergistic oxidation, but also utilizes the anoxic environment of the homogenization reaction tank to achieve the second-stage deep denitrification.

[0039] (3) A carbon-based composite material with a large specific surface area, rich pore interface and surface loaded with variable valence metal manganese and magnesium oxides was adopted. This material can provide abundant adsorption and reaction sites for microorganisms and organic matter, which not only increases the concentration of activated sludge, but also significantly increases the diversity of microorganisms. Moreover, this material can directly generate free radicals and can achieve synergistic coupling between chemicals and microorganisms. It has efficient simultaneous nitrogen and phosphorus removal and high efficiency removal rate of new pollutants, thus improving the deep removal capacity of nitrogen and phosphorus pollutants in wastewater.

[0040] (4) It realizes the recycling and reuse of magnetic carbon-based composite materials, which helps to save wastewater treatment costs.

[0041] (5) Magnesium oxides on the interface can mineralize inorganic phosphorus in situ to form relatively stable magnesium phosphate minerals, which exist in sludge, thus facilitating the resource utilization of phosphorus in sludge. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of a nitrogen- and phosphorus-containing wastewater treatment system in one embodiment of the present invention.

[0043] Figure 2 The image shows the characterization spectrum of a carbon-based composite material in one embodiment of the present invention, wherein (a) is a Fourier transform infrared spectrum and (b) is an XPS spectrum.

[0044] Figure 3 This is a schematic diagram of phosphorus loading after phosphorus removal from a carbon-based composite material in one embodiment of the present invention.

[0045] Attached diagram labels: 1-Inlet; 2-Outlet; 3-Pre-anoxic tank; 4-Inclined plate sedimentation tank; 5-Anaerobic tank; 6-Anoxic tank; 7-Equalization reaction tank; 8-Synergistic oxidation tank; 9-Bottom tank; 10-Separation tank; 11-Recirculation tank; 12-Storage tank; 13-Material transport pipeline; 14-Material return pipeline. Detailed Implementation

[0046] The present invention will be described in detail below with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0047] Example 1

[0048] See Figure 1This invention provides a nitrogen and phosphorus wastewater treatment system, including a pre-anoxic tank 3, an inclined plate sedimentation tank 4, an anaerobic tank 5, an anoxic tank 6, a homogenization reaction tank 7, two co-oxidation tanks 8, two storage tanks 12, a material transport pipeline, and an outlet 2. The inlet 1 of the nitrogen and phosphorus wastewater treatment system is connected to the anaerobic tank 5, and the anaerobic tank 5, anoxic tank 6, homogenization reaction tank 7, and co-oxidation tank 8 are connected in sequence. The inclined plate sedimentation tank 4 is provided with a sludge discharge outlet and a supernatant discharge outlet. The sludge discharge outlet is connected to the pre-anoxic tank 3, and the supernatant discharge outlet is connected to the co-oxidation tank 8. The pre-anoxic tank, anaerobic tank, and anoxic tank are all equipped with stirring devices. The pre-anoxic tank 3 is connected to the anaerobic tank 5 via a pipeline. The outlet of the storage tank 12 is connected to the material transport pipeline 13, which is connected to the homogenization reaction tank 7. The homogenization reaction tank 7 is equipped with several stirring groups. The co-oxidation tank 8 is equipped with a mixed liquor return channel, a sludge return channel, and several aeration devices. The mixed liquor return channel is connected to the anoxic tank 6, the sludge return channel is connected to the inclined plate sedimentation tank 4, and the outlet of the co-oxidation tank 8 is connected to the effluent outlet 2. The two storage tanks 12 are interconnected via pipelines.

[0049] The treatment reaction system also includes two reflux tanks 11 and two separation tanks 10. The two reflux tanks 11 are interconnected by pipes, and the two separation tanks 10 are interconnected by pipes. A bottom tank 9 is provided within the co-oxidation tank 8, located in the middle of the co-oxidation tank 8. A sludge pump is installed in the bottom tank 9, and the outlet of the sludge pump is connected to the separation tank 10. The separation tank 10 is equipped with a backwash water pump and a magnetic field device (not shown in the figure) that can be turned on or off. The discharge port of the separation tank is connected to one end of a material return pipe 14, and the other end of the material return pipe 14 is connected to the reflux tank 11. The outlet of the reflux tank 11 is connected to a material transport pipe 13. A sludge discharge port is provided on the co-oxidation tank 8. The inlet of the sludge discharge port is connected to the outlet of the sludge pump, and the outlet of the sludge discharge port is connected to the separation tank 10.

[0050] The magnetic field device includes a magnetic induction coil disposed in the separation tank and a switching device for controlling the energization and de-energization of the magnetic induction coil.

[0051] The outlets of the reflux tank 11 and the storage tank 12 are equipped with diaphragm metering pumps, and the outlets of the diaphragm metering pumps are connected to the material transport pipeline 13.

[0052] The bottom surface of the synergistic oxidation tank 8 has a slope of 6°, and the bottom areas on both sides of the bottom tank gradually slope downward towards the bottom tank.

[0053] Example 2

[0054] 1.1 Preparation of carbon-based composite materials

[0055] Dry plant-derived biomass (Myriophyllum verticillatum) with a mesh size of 60-80 was mixed with manganese acetate and potassium permanganate in an aqueous solution at a ratio of 200 g: 1.5 mol: 1 mol. The mixture was stirred for 60 min, washed, filtered, and freeze-dried to obtain manganese-loaded biomass. The manganese-loaded biomass was then mixed with magnesium chloride at a mass ratio of 1:1 and ground to obtain a sample powder. The sample powder was pyrolyzed at 700 °C for 2.5 h under an argon atmosphere to obtain biochar loaded with manganese and magnesium bimetals, i.e., a carbon-based composite material. The specific surface area of ​​the carbon-based composite material is greater than 180 m². 2 / g, the mass ratio of biochar to manganese oxide and magnesium oxide is 1:0.68:1.14.

[0056] 1.2 Characterization of carbon-based composite materials

[0057] The surface functional groups of the manganese-magnesium-containing carbon-based composite material (Mn / Mg@MV) were identified using Fourier transform infrared spectroscopy (FTIR, Thermo Scientific Nicolet iS20). The results are as follows: Figure 2 As shown in (a), the Mn / Mg@MV surface has abundant functional groups: OH groups (~3430 cm⁻¹), aromatic CO bonds (~1048 cm⁻¹), aromatic C=C (~1420 cm⁻¹), carbonyl C=O (~1631 cm⁻¹), Mn-O and Mg-O groups (~482 cm⁻¹), proving that the deposition of metal elements Mn and Mg was successful.

[0058] XPS spectroscopy (Thermo Scientific K-Alpha) was used to further understand the chemical composition and surface state of Mn / Mg@MV, such as... Figure 2 As shown in (b), the peaks at 285.39, 532.22, 643.12, and 1304.45 eV correspond to C1s, O 1s, Mn 2p, and Mg 2p, respectively. This indicates that the Mn-Mg bimetallic compound was successfully loaded onto the biochar surface. Further investigation of the high-resolution spectral peaks of Mn 2p (not shown) revealed the presence of three Mn substances (Mn(IV), Mn(III), and Mn(II)), located at 645.03, 642.86, and 641.56 eV, respectively. This indicates that the biochar surface is uniformly doped with abundant Mn elements of different valence states, which may play an important role in the activation of the oxidant and ensure that the carbon-based composite material can fully exert its unique role in the subsequent degradation of organophosphorus compounds.

[0059] Example 3

[0060] The carbon-based composite material prepared in Example 2 was used to treat mixed phosphorus wastewater (TPhP wastewater and orthophosphate wastewater), and the carbon-based composite material was recovered. Available phosphorus on the carbon-based composite material was extracted sequentially using deionized water, NaOH solution (0.1 mol / L), NaHCO3 solution (0.5 mol / L), and HCl solution (1 mol / L); during extraction, the solid-liquid ratio was controlled at 1 g:150 mL. The pretreated simulated wastewater parameters were: pH 6-9, TP content 50 mg / L, and water temperature 15℃. The results are as follows: Figure 3 As shown, the prepared carbon-based composite material can remove phosphorus, and the magnesium loaded on the surface has a high adsorption capacity and selectivity for phosphate. The magnesium oxide on the interface can mineralize inorganic phosphorus in situ to form relatively stable magnesium phosphate minerals, which can be used to prepare magnesium phosphate / magnesium ammonium phosphate slow-release phosphate fertilizer in a resource-based manner.

[0061] Example 4

[0062] Using the nitrogen and phosphorus wastewater treatment system provided in Embodiment 1 of the present invention (see...) Figure 1 The carbon-based composite material prepared in Example 2 was used to treat municipal wastewater. In this example, the pH value of the municipal wastewater was 6-9, and the water quality index was COD. cr The concentrations are: 300 mg / L for nitrogen and phosphorus wastewater, 170 mg / L for BOD5, 150 mg / L for suspended solids (SS), 15 mg / L for NH3-N, 25 mg / L for total nitrogen (TN), and 5 mg / L for total phosphorus (TP). The water temperature is 15℃. The nitrogen and phosphorus wastewater treatment system uses two synergistic oxidation tanks that alternately receive water intermittently, allowing for continuous system operation. The specific steps are as follows:

[0063] Municipal wastewater sequentially passes through a coarse screen, a wastewater lifting pump station, a fine screen, and a grit chamber before entering the anaerobic tank 5 through inlet 1. Sludge from the pre-anoxic tank 3 is discharged into the anaerobic tank 5 via a pipeline. The nitrogen- and phosphorus-laden wastewater and sludge in the anaerobic tank 5 are mixed for phosphorus release before being discharged into the anoxic tank 6 for denitrification. The mixed liquor from the anoxic tank 6 is then discharged into the homogenization reaction tank 7. The carbon-based composite material prepared in Example 2 is pre-stored in storage tank 12 and added at a rate of 6.5 kg / ton of wastewater via a diaphragm metering pump to the material transport pipeline 13, and then added to the homogenization reaction tank 7. The stirring group in the homogenization reaction tank 7 is activated to continuously stir and mix the wastewater and suspended solids, causing the carbon-based composite material, microorganisms, sludge, and organic matter to undergo a homogenization reaction, achieving uniform adhesion and obtaining a homogenized mixed liquor. The homogenized mixed liquor is discharged into the co-oxidation tank 8, and the aeration device is turned on for aeration oxidation treatment at an aeration flow rate of Q = 10 m³ / min. During aeration, part of the mixed liquor is returned to the anoxic tank 8 through the mixed liquor return channel. After the aeration reaction in oxygen tank 6 is completed, the aeration is slowly shut off to allow the mixed liquor in the tank to settle and separate, resulting in treated liquid and sludge. The outlet of the co-oxidation tank 8 is connected to the effluent outlet 2, and the treated liquid is discharged from the effluent outlet for further treatment. Part of the sludge is returned to the inclined plate sedimentation tank 4 through the sludge return channel, and part of the sludge is fed into the sludge pump of the separation tank 10. The magnetic field device is turned on, causing the carbon-based composite material to adhere to the magnetic field device, resulting in residual sludge. After the residual sludge is completely discharged outside the separation tank (it can be sent to the sludge dewatering workshop for further dewatering), the magnetic field device is turned off, and the backwash water pump is turned on to wash the attached carbon-based composite material, causing it to accumulate in the separation tank 10, resulting in carbon-based composite material slurry. The carbon-based composite material slurry is then transported to the return tank through the material return pipe 14 for recycling. The sludge in the inclined plate sedimentation tank 4 is settled to obtain concentrated sludge and supernatant from the inclined plate. The concentrated sludge is discharged into the pre-anoxic tank 3 through the sludge discharge outlet, and the supernatant from the inclined plate is returned to the co-oxidation tank 8 through the supernatant discharge outlet.

[0064] The TN content in the treated liquid (i.e., effluent) discharged from the synergistic oxidation tank 8 was measured to be 9 mg / L and the TP content was 0.4 mg / L, meaning that the TN removal rate in this embodiment was 64% and the TP removal rate was 92%.

[0065] Example 5

[0066] The process of collecting and treating organic wastewater from a certain area is basically the same as that in Example 4, with the only difference being:

[0067] (1) Organic wastewater quality indicators: pH value 6~9, COD cr Content 200mg / L, BOD5 content 90mg / L, suspended solids (SS) content 110mg / L, NH3-N content 15mg / L, TN content 20mg / L, TP content 12.2mg / L, water temperature 11℃.

[0068] (2) Carbon-based composite material addition amount: 4.5 kg / cubic meter of wastewater; microbial carbon source: glucose, 0.03 kg / cubic meter of wastewater. The carbon-based composite material is pre-stored in storage tank 12.

[0069] The TN content in the effluent of this embodiment was measured to be 6.5 mg / L, and the TP content was 0.48 mg / L, meaning that the TN removal rate of this embodiment was 65% and the TP removal rate was 96%.

[0070] Example 6

[0071] The process of collecting and treating organic wastewater from a certain area is basically the same as that in Example 4, with the only difference being:

[0072] (1) Organic wastewater quality indicators: pH value 6~9, COD cr Content 253 mg / L, BOD5 content 110 mg / L, suspended solids (SS) content 182 mg / L, NH3-N content 24 mg / L, TN content 38 mg / L, TP content 3.5 mg / L, water temperature 15℃.

[0073] (2) Carbon-based composite material addition: 6.5 kg / m³ of wastewater; microbial carbon source: sodium acetate, 0.05 kg / m³ of wastewater. The carbon-based material is pre-stored in storage tank 12.

[0074] (3) Sodium periodate was added to the synergistic oxidation tank 8 as an oxidant. The concentration of sodium periodate in the mixed system was 2.0 mmol / L.

[0075] The TN content in the effluent of this embodiment was measured to be 10 mg / L, and the TP content was 0.1 mg / L, meaning that the TN removal rate of this embodiment was 73.7%, and the TP removal rate was 97%. The recovery rate of the carbon-based composite material (calculated as the ratio of the carbon-based composite material recovered in the separation tank to the amount of carbon-based composite material added) was 93.34 wt%.

[0076] Comparative Example 1

[0077] Example 6 was repeated, except that unmodified biochar was used instead of the carbon-based composite material.

[0078] The TN content in the effluent of this embodiment was measured to be 13.69 mg / L, and the TP content was 0.5 mg / L, meaning that the TN removal rate of this embodiment was 63.9% and the TP removal rate was 85.7%.

[0079] Comparative Examples 2-7, Examples 7-9

[0080] Repeat Example 6, except for the parameters shown in Table 1.

[0081] Table 1

[0082]

[0083] As a result, the TN removal rate of Comparative Example 2 was measured to be 68.95%, and the TP removal rate was 92%. The recovery rate of the carbon-based composite material was 81.75%.

[0084] As a result, the TN removal rate of Example 7 was measured to be 77.11%, and the TP removal rate was 97.15%. The recovery rate of the carbon-based composite material was 93.98%.

[0085] The results showed that the TN removal rate of Comparative Example 3 was 77.84%, and the TP removal rate was 95.72%. The recovery rate of the carbon-based composite material was 93.34%.

[0086] As a result, the TN removal rate of Comparative Example 4 was measured to be 64.94%, and the TP removal rate was 88.86%. The recovery rate of the carbon-based composite material was 79.27%.

[0087] As a result, the TN removal rate in Example 8 was measured to be 81.06%, and the TP removal rate was 97.72%. The recovery rate of the carbon-based composite material was 94.72%.

[0088] As a result, the TN removal rate of Comparative Example 5 was measured to be 81.32%, and the TP removal rate was 94.62%. The recovery rate of the carbon-based composite material was 94.88%.

[0089] As a result, the TN removal rate of Comparative Example 6 was measured to be 76.2%, and the TP removal rate was 92.29%. The recovery rate of the carbon-based composite material was 92.98%.

[0090] As a result, the TN removal rate of Example 9 was measured to be 72.26%, and the TP removal rate was 98%. The recovery rate of the carbon-based composite material was 90.53%.

[0091] As a result, the TN removal rate of Comparative Example 7 was measured to be 70.63%, and the TP removal rate was 98%. The recovery rate of the carbon-based composite material was 84.75%.

[0092] The above embodiments should be understood as being used only to illustrate the present invention more clearly, and not to limit the scope of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope defined by the appended claims.

Claims

1. A method for treating nitrogen and phosphorus wastewater, characterized in that, A nitrogen-phosphorus wastewater treatment system is used. Sludge from the pre-anoxic tank is discharged into the anaerobic tank through a pipeline. Wastewater with a pH of 6-9 enters the anaerobic tank through the inlet. The wastewater and sludge in the anaerobic tank are mixed and undergo a phosphorus release reaction before being discharged into the anoxic tank for denitrification. The mixed liquor in the anoxic tank is then discharged into a homogenization reaction tank. An appropriate amount of carbon-based composite material from a storage tank is added to the homogenization reaction tank through a material transport pipeline. The stirring group is started to stir the carbon-based composite material and the mixed liquor until they are evenly mixed to obtain a homogenized mixed liquor. The homogenized mixed liquor is discharged into a co-oxidation tank, and the aeration device is turned on for aeration oxidation treatment. During the aeration process, part of the mixed liquor is returned to the anoxic tank through the mixed liquor return channel. After the aeration reaction is completed, the aeration device is turned off, and the mixed liquor is subjected to sedimentation separation to obtain treated liquid and sludge. The treated liquid is discharged through the outlet for further treatment, and part of the sludge is returned to the inclined plate sedimentation tank through the sludge return channel, while part of the sludge is discharged outside the nitrogen and phosphorus wastewater treatment system. After sedimentation, the sludge in the inclined plate sedimentation tank is concentrated sludge and supernatant liquid. The concentrated sludge is discharged into the pre-anoxic tank through the sludge discharge outlet, and the supernatant liquid is discharged into the synergistic oxidation tank through the supernatant discharge outlet. The carbon-based composite material is prepared by the following steps: 60-80 mesh dried plant-derived biomass is mixed with divalent manganese salt and permanganate in an aqueous solution at a ratio of 200-500 g: 1.5-2.5 mol: 1-1.5 mol. The mixed solution is washed, filtered, and freeze-dried to obtain manganese-loaded biomass. Manganese-loaded biomass and inorganic magnesium salts were mixed and ground at a mass ratio of 1:1 to 1.6 to obtain sample powder. The sample powder was then pyrolyzed at 650 to 750°C for 2 to 3 hours under an argon atmosphere to obtain biochar loaded with manganese and magnesium bimetals, i.e., the carbon-based composite material.

2. The nitrogen and phosphorus wastewater treatment method according to claim 1, characterized in that, The carbon-based composite material uses biochar as a carrier, with manganese oxides and magnesium oxides loaded on the surface of the biochar; based on the COD in the wastewater... cr The content of NH3-N, TP and BOD5 / COD cr The ratio adjustment is the amount of carbon-based composite material added per cubic meter of wastewater, A0, where A0 = baseline value A1 + additional value A2; The criteria for adding the baseline value A1 are as follows: COD cr ≤100mg / L,A1=2kg / m 3 ;100mg / L<COD cr ≤200mg / L,A1=4kg / m 3 ;200mg / L<COD cr ≤300mg / L,A1=6kg / m 3 ; CODE cr >300mg / L,A1=2*COD cr / 100; The additional value A2 ≥ 0 kg / m 3 .

3. The nitrogen and phosphorus wastewater treatment method according to claim 2, characterized in that, The additional value A2 is 0~4 kg / m 3 .

4. The nitrogen and phosphorus wastewater treatment method according to claim 2, characterized in that, The criteria for determining the value of the additional value A2 are as follows: (1) When BOD5 / COD cr > 0.58, and / or, when TP < 12 mg / L, A2 = 0; (2) When BOD5 / COD cr When the concentration of TP is 0.45~0.58, and / or when the concentration of TP is 12~15 mg / L, A2 = 0.5 kg / m 3 ; (3) When BOD5 / COD cr When the concentration of TP is 0.30~0.45, and / or when the concentration of TP is 15~19 mg / L, A2 = 1 kg / m 3 ; (4) When BOD5 / COD cr When A2 is < 0.3 and / or TP > 19 mg / L, A2 ≥ 4 kg / m 3 .

5. The nitrogen and phosphorus wastewater treatment method according to claim 2, characterized in that, The specific surface area of ​​the carbon-based composite material is not less than 180 m². 2 / g, wherein the mass ratio of biochar to manganese oxide and magnesium oxide is 1:0.6 ~ 0.95:0.95 ~1.

6.

6. The nitrogen and phosphorus wastewater treatment method according to claim 1, characterized in that, When the BOD5 / TN ratio of wastewater is ≤ 3.5, and / or when the wastewater temperature is less than 12°C, a carbon source is added; the carbon source is at least one of glucose, sodium acetate, methanol, and ethanol; the dosage of the carbon source is 0.01 ~ 0.05 kg / m³. 3 .

7. The nitrogen and phosphorus wastewater treatment method according to claim 1, characterized in that, Part of the sludge is fed into the separation tank, and the magnetic field device is turned on to make the carbon-based composite material adhere to the magnetic field device, resulting in the remaining sludge. After the remaining sludge is completely discharged out of the separation tank, the magnetic field device is turned off, and the backwash water pump is turned on to wash the attached carbon-based composite material, causing it to accumulate in the separation tank to obtain a carbon-based composite material slurry. The carbon-based composite material slurry is then transported to the return tank through the material return pipeline.

8. The nitrogen and phosphorus wastewater treatment method according to claim 1, characterized in that, The nitrogen and phosphorus wastewater treatment system includes a pre-anoxic tank, an inclined plate sedimentation tank, an anaerobic tank, an anoxic tank and an outlet, a homogenization reaction tank, a co-oxidation tank, material transport pipelines, and a storage tank for storing carbon-based composite materials; the inlet of the nitrogen and phosphorus wastewater treatment system is connected to the anaerobic tank, and the anaerobic tank, anoxic tank, homogenization reaction tank, and co-oxidation tank are connected in sequence; the inclined plate sedimentation tank is equipped with a sludge discharge outlet and a supernatant discharge outlet, the sludge discharge outlet is connected to the pre-anoxic tank, and the supernatant discharge outlet is connected to the co-oxidation tank; The pre-anoxic tank, anaerobic tank, and anoxic tank are all equipped with stirring devices. The pre-anoxic tank is connected to the anaerobic tank via a pipeline. The outlet of the storage tank is connected to the material transport pipeline, which is connected to the homogenization reaction tank. The homogenization reaction tank is equipped with several stirring groups. The synergistic oxidation tank is equipped with a mixed liquor return channel, a sludge return channel, and several aeration devices. The mixed liquor return channel is connected to the anoxic tank, the sludge return channel is connected to the inclined plate sedimentation tank, and the outlet of the synergistic oxidation tank is connected to the effluent outlet. The nitrogen and phosphorus wastewater treatment system also includes a return tank and a separation tank; The synergistic oxidation tank is equipped with a bottom tank, and a sludge pump is installed in the bottom tank. The outlet of the sludge pump is connected to the separation tank. The separation tank is equipped with a backwash water pump and a magnetic field device that can be turned on or off. The discharge port of the separation tank is connected to one end of the material return pipeline, and the other end of the material return pipeline is connected to the return tank. The outlet of the return tank is connected to the material transport pipeline. The magnetic field device includes a magnetic induction coil disposed in the separation tank and a switching device for controlling the energization and de-energization of the magnetic induction coil.

9. The nitrogen and phosphorus wastewater treatment method according to claim 8, characterized in that, The outlets of the reflux tank and the storage tank are equipped with diaphragm metering pumps, and the outlets of the diaphragm metering pumps are connected to the material transport pipelines.

10. The nitrogen and phosphorus wastewater treatment method according to claim 1, characterized in that, The ratio of dried plant-derived biomass to divalent manganese salt and permanganate is 300~400 g: 1.8~2.3 mol: 1.1~1.4 mol.

11. The nitrogen and phosphorus wastewater treatment method according to claim 1, characterized in that, The mass ratio of manganese-loaded biomass to inorganic magnesium salts is 1:1.1~1.4.

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