Nitrogen and phosphorus recovery treatment method and device for activated carbon preparation wastewater

Abstract

The invention discloses a nitrogen and phosphorus recovery treatment method and device for activated carbon preparation wastewater, and relates to the technical field of activated carbon preparation wastewater, and the method comprises the following steps: S1, premixing reaction: introducing wastewater generated by an activated carbon phosphoric acid activation method into a premixing pool, adding a mixed reagent of calcium oxide and magnesium oxide into the wastewater, pre-reaction is carried out under the stirring condition, and the reaction time is longer than 30 minutes; step S2, suspension mixing crystallization reaction: pumping the pre-reacted wastewater into a suspension mixing reaction tank, enabling the wastewater to uniformly flow upwards from the bottom of the suspension mixing reaction tank through an inclined plate water distributor, and simultaneously introducing air into the bottom of the suspension mixing reaction tank for aeration. According to the invention, through the unique process design, the processes of reaction, crystallization and mud-water separation are successfully coordinated and optimized in a highly intensive system, and the core defects of the traditional process in the four aspects of land occupation, stability, cost and recycling are synchronously solved.

Description

Technical Field

[0001] This invention relates to the field of activated carbon preparation wastewater technology, and in particular to a method and apparatus for nitrogen and phosphorus recovery treatment of activated carbon preparation wastewater. Background Technology

[0002] Activated carbon is a widely used porous adsorbent material with numerous preparation methods. Among them, the phosphoric acid activation method has become one of the mainstream processes due to its mature technology and excellent product performance. During the activation process, a large amount of high-concentration process wastewater is generated, mainly including the activation waste liquid periodically discharged from the reactor and the spray wastewater from the phosphoric acid tail gas purification system. Typical characteristics of this type of wastewater are: relatively small volume but extremely high pollutant concentration; it is usually strongly acidic (pH value can reach 1-3), containing high concentrations of phosphates (total phosphorus TP can reach several thousand milligrams per liter), high concentrations of ammonia nitrogen (NH3-N, originating from raw materials or activation side reactions), high chemical oxygen demand (COD, mainly from the decomposition products of carbonaceous raw materials and phosphate esters), high salinity (mainly phosphates, sulfates, and small amounts of chlorides), and a large amount of inorganic suspended solids.

[0003] Currently, for this type of high-concentration, complexly polluted wastewater, the industry generally adopts a combined process route of "physicochemical pretreatment + biological deep treatment". Specifically, firstly, alkaline substances such as lime (Ca(OH)2) or liquid alkali (NaOH) are added to neutralize the wastewater and raise its pH value, allowing some phosphates to precipitate and be removed as calcium phosphate precipitates. Then, coagulants and flocculants such as polyaluminum chloride (PAC) and polyacrylamide (PAM) are added for coagulation and flocculation, further removing colloidal and suspended phosphorus and some organic matter. Solid-liquid separation is achieved through sedimentation. The supernatant after pretreatment still has high COD and ammonia nitrogen concentrations, requiring subsequent biological treatment systems, such as anaerobic / aerobic (A / O) processes, sequencing batch reactors (SBR), or membrane bioreactors (MBR), to utilize the metabolic action of microorganisms to degrade organic matter and perform nitrification and denitrification to remove ammonia nitrogen. Although the above conventional processes can achieve compliant discharge under certain conditions, their inherent technical defects are becoming increasingly prominent when treating activated carbon-phosphate activated wastewater. The process is lengthy and requires a large area: from adjustment, neutralization, coagulation, flocculation, sedimentation to multi-stage biological treatment (including anaerobic, aerobic, sedimentation and other units), the entire system includes numerous structures and equipment, and complex pipelines, resulting in a huge area occupied by the wastewater treatment plant. This is a heavy burden for existing plants that are short of land or need to be upgraded.

[0004] The system is costly and uneconomical: the physicochemical stage requires large amounts of alkaline reagents and coagulants; the biological stage requires continuous aeration and oxygen supply (high energy consumption) and generates a large amount of excess sludge that needs to be treated. More importantly, the instability of the system leads to frequent adjustments, excessive addition of reagents, and sludge disposal costs, which further increase the operating cost throughout the entire life cycle.

[0005] The failure to recycle resources poses a risk of secondary pollution: Current technologies treat nitrogen (ammonia nitrogen) and phosphorus (phosphate) with recycling value in wastewater merely as "pollutants," converting them into phosphorus-containing chemical sludge through chemical precipitation or microbial transformation, ultimately ending up in residual sludge. This sludge has a complex composition (containing heavy metals, recalcitrant organic matter, etc.), low nutritional value, and may possess polluting characteristics, typically disposed of as hazardous waste through landfill or incineration. This not only wastes valuable phosphorus and nitrogen resources (phosphorus is a non-renewable strategic resource) but also results in "pollution transfer," posing a potential risk of secondary environmental pollution, which is inconsistent with the current development concepts of "zero-waste cities" and a circular economy.

[0006] Therefore, developing a new treatment technology and equipment that can efficiently and simultaneously remove nitrogen and phosphorus, has a simple process flow, and enables the resource recovery of nitrogen and phosphorus, in order to fundamentally solve the problem of high-concentration wastewater treatment in the activated carbon preparation industry, has become a technical bottleneck that urgently needs to be overcome in this field.

[0007] Based on the above, we have designed a nitrogen and phosphorus recovery treatment method for activated carbon preparation wastewater to solve the above problems. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for nitrogen and phosphorus recovery treatment of activated carbon preparation wastewater.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for nitrogen and phosphorus recovery treatment of activated carbon preparation wastewater includes the following steps: Step S1, Premixing reaction: The wastewater generated by the activated carbon phosphoric acid activation method is introduced into the premixing tank, and a mixture of calcium oxide and magnesium oxide is added to the wastewater. The pre-reaction is carried out under stirring conditions for more than 30 minutes. Step S2, Suspension Crystallization Reaction: The pre-reacted wastewater is pumped into the suspension reaction tank. The wastewater flows evenly upward from the bottom of the suspension reaction tank through an inclined plate water distributor. At the same time, air is introduced into the bottom of the suspension reaction tank for aeration. The air-to-water volume ratio is controlled at 10:1 to 30:1. The upward flow velocity of the wastewater after passing through the area of ​​the inclined plate water distributor is controlled at 3 to 7 m / h. This allows the nitrogen and phosphorus-containing crystal particles formed in the wastewater to form and remain suspended in the suspension reaction tank, forming a suspended sludge layer. Step S3, Solid-liquid separation: The suspended sludge is discharged from the bottom of the suspension reaction tank and sent to a centrifuge for solid-liquid separation; Step S4, Product Disposal: Collect the supernatant and sludge separated by the centrifuge. The supernatant enters the subsequent processing unit, and the sludge is dewatered and used as a soil conditioner or phosphate fertilizer for resource utilization.

[0010] Preferably, in step S1, the mass ratio of calcium oxide to magnesium oxide in the mixed agent is 3:1 to 12:1.

[0011] Preferably, in step S1, the mixture of calcium oxide and magnesium oxide is added in the form of a slurry with a mass concentration of 10% to 20%.

[0012] Preferably, in step S2, the inclined plate water distributor includes at least one set of inclined baffles disposed above, and the baffles are provided with a plurality of water distribution holes; after being distributed, the wastewater flows out through the water distribution holes on the baffles and collides and mixes with the aeration airflow from bottom to top in the inclined plate area of ​​the baffles 501.

[0013] Preferably, in step S3, the rotation speed of the centrifuge during solid-liquid separation is 3000 ~ 6000 r / min.

[0014] A nitrogen and phosphorus recovery and treatment device for activated carbon preparation wastewater includes: The premixing tank is equipped with a dosing system and a stirrer for carrying out the premixing reaction; The suspension reaction tank is connected to the premixing tank via a lift pump. Inside, from bottom to top, there are inclined plate water distributors, a mixing aeration system and an effluent weir, which are used for suspension crystallization reaction. One end of the mixing aeration system extends to the outside of the suspension reaction tank and is connected to a mixing blower. A centrifugal separator, the inlet of which is connected to the bottom sludge discharge port of the suspension reaction tank, is used for solid-liquid separation. A sludge discharge pump is connected between the centrifugal separator and the sludge tank. The sludge tank is connected to the sludge cake outlet of the centrifuge and is used to receive and dispose of dewatered sludge.

[0015] Preferably, the inclined plate water distributor includes at least one set of inclined baffles disposed above it, and the baffles are provided with a plurality of water distribution holes.

[0016] Preferably, the dosing system is used to add a mixed slurry of calcium oxide and magnesium oxide in a mass ratio of 3:1 to 12:1.

[0017] Preferably, the device is used in the treatment of reactor wastewater or tail gas spray wastewater generated in the phosphoric acid activation process of activated carbon preparation.

[0018] Compared with the prior art, the beneficial effects of the present invention are: The process is compact and requires little space: the traditional multi-step reaction precipitation is integrated into a one-step core reaction of "premixing-suspension crystallization", and with efficient centrifugal separation, the system footprint is reduced by more than 60%.

[0019] Strong resistance to shock loads and stable operation: The entire process is physical and chemical treatment, completely unaffected by the effects of high salinity and highly toxic organic matter on microorganisms, and the nitrogen and phosphorus concentrations in the effluent are stable and controllable.

[0020] Simultaneous and efficient nitrogen and phosphorus removal: Through the combination of CaO / MgO reagents and suspension crystallization process, efficient and simultaneous removal of ammonia nitrogen and phosphate is achieved in a single reactor (removal rate >94%), creating favorable conditions for subsequent biochemical treatment.

[0021] Achieving resource recovery and reducing treatment costs: Pollutants are converted into high-purity struvite fertilizer, making the resource-based product economically valuable. The dosage is customized (using inexpensive industrial-grade calcium oxide and magnesium oxide), and the suspension process improves reagent utilization. The costs of aeration, carbon source, and sludge disposal in the biological system are eliminated, resulting in an overall treatment cost reduction of approximately 30-40% compared to traditional processes.

[0022] The innovative effect of "suspension crystallization": The key to this invention is the synergistic design of the inclined plate water distributor and aeration. It is not only a mixing device, but also a "crystallizer". The dynamic suspension environment it creates is a necessary condition for forming high-quality, easily separable crystallized products, which cannot be achieved by conventional stirred reactions or sedimentation tanks.

[0023] Through its unique process design, this invention successfully optimizes the processes of "reaction", "crystallization" and "mud-water separation" in a highly integrated system, simultaneously solving the core defects of traditional processes in terms of land use, stability, cost, and resource utilization. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a nitrogen and phosphorus recovery treatment method for activated carbon preparation wastewater proposed in this invention. Figure 2 This is a diagram showing the connection structure of an apparatus for nitrogen and phosphorus recovery treatment of activated carbon preparation wastewater according to the present invention. Figure 3 This is a schematic diagram of the inclined plate water distributor for a nitrogen and phosphorus recovery treatment method for activated carbon preparation wastewater proposed in this invention.

[0025] In the diagram: 1 Premixing tank, 2 Agitator, 3 Lifting pump, 4 Suspended reaction tank, 5 Inclined plate water distributor, 501 Water baffle, 502 Water distribution hole, 503 Water distribution pipe, 6 Mixing aeration system, 7 Mixing blower, 8 Centrifugal separator, 9 Sludge pump. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0027] This invention provides a method and apparatus for nitrogen and phosphorus recovery and treatment of wastewater (high phosphorus, high ammonia nitrogen, high salinity, low pH) from the phosphoric acid activation process in activated carbon preparation. Its core innovation lies in achieving efficient synergistic removal and resource conversion of nitrogen and phosphorus pollutants within a compact reaction unit through a process combination of "directional chemical precipitation - suspension crystallization enhancement - high-efficiency centrifugal separation." This solves the problems of traditional "physicochemical + biochemical" processes, which are characterized by long flow rates, large footprints, poor adaptability to high-salinity wastewater, unstable operation, and lack of resource recovery.

[0028] Example 1 Reference Figure 1-3 A typical method for nitrogen and phosphorus recovery treatment of activated carbon preparation wastewater: 1. Wastewater Quality: This example treats mixed wastewater (including reactor flushing water and tail gas spray tower drainage) generated from the phosphoric acid activation process of an activated carbon production plant. Typical wastewater quality is as follows: pH=2.5, COD=8500 mg / L, ammonia nitrogen (NH3-N)=650 mg / L, total phosphorus (TP, as PO4) 3 Total dissolved solids (TDS) = 3200 mg / L, total dissolved solids (TDS) = 45000 mg / L, and suspended solids (SS) = 1500 mg / L.

[0029] Processing device: Refer to Figure 2 The device includes a premixing tank 1, a suspension reaction tank 4, a centrifuge 8, and a sludge tank 10 connected in sequence.

[0030] Among them, the premixing tank 1 is made of steel-lined PE anti-corrosion material, with an effective volume of 10m³. 3 The tank is equipped with a 7.5kW coagulation mixer 2 (corresponding to the mixer 2 in the claim), which uses double-layer blades to ensure that the mixing intensity reaches approximately 70 W / m. 3 The rotation speed is 350 r / min. A pH meter, ORP meter and level gauge are installed on the side wall of the tank, and a dosing system is installed on the top of the tank, including two reagent dissolution tanks with agitators and two metering pumps.

[0031] Suspended mixing reactor 4 is made of corrosion-resistant carbon steel, designed as a vertical flow reactor, with an effective volume of 15m³. 3 The height-to-diameter ratio is 3:1. Its core component is the inclined plate water distributor 5 located at the bottom of the pool, with the structure as follows: Figure 2 As shown. The water distributor consists of a horizontally arranged water distribution pipe 503 and two sets of inclined baffles 501 above it. The baffles 501 are at a 60° angle to the horizontal plane, and water distribution holes 502 with a diameter of 20mm are evenly distributed on the plates. A perforated pipe mixing aeration system 6 is provided at the bottom of the pool. As a mixing aeration system 6, it consists of a mixing blower 7 (air volume 3.5 m³ / s). 3 Air supply is provided at a rate of 100 m / min (air pressure 49 kPa). A sawtooth-shaped outlet weir is provided at the top of the pool.

[0032] The centrifuge 8 is a horizontal screw sedimentation centrifuge with a drum diameter of 450mm, a length-to-diameter ratio of 4:1, a maximum speed of 4500r / min, and an adjustable differential speed. Its feed inlet is connected to the sludge discharge port at the bottom of the suspension reaction tank 4 via pipes and valves. The supernatant outlet pipe is connected to the subsequent biological treatment unit (such as a UASB or A / O tank), and the solid phase outlet is connected to the sludge tank (with a screw press dewatering machine) via a sludge discharge pump 9.

[0033] Processing steps and parameter control: Step S1: Transfer the collected wastewater to a 2 m... 3 A flow rate of / h is pumped into premixing tank 1. Simultaneously, a pre-prepared CaO / MgO mixed reagent slurry is continuously added via a dosing system. The slurry concentration is 15% (mass fraction), with a CaO to MgO mass ratio of 8:1. The dosage is automatically controlled via pH meter feedback to maintain the reaction pH in premixing tank 1 between 9.5 and 10.0. Coagulation mixer 2 is started, and the reaction proceeds under strong stirring, with the hydraulic retention time (HRT) controlled at 50 minutes. The main effects during this stage are: (a) CaO neutralizes the acidity of the wastewater, increasing pH and providing dissolved CaO. 2+ (b) MgO dissolves slowly and simultaneously to provide Mg 2 (c) Initial formation of microcrystalline nuclei such as calcium phosphate and magnesium phosphate. Innovation highlights: the use of a specific ratio of CaO / MgO mixture instead of a single alkali or magnesium source. CaO rapidly adjusts pH, resulting in low-cost and high-volume phosphate removal; MgO slowly releases Mg... 2 ⁺ can work synergistically with subsequent steps to remove phosphate and ammonia nitrogen, avoiding excessive local supersaturation that could lead to amorphous precipitates. Instead, it guides the formation of easily growing crystals and provides continuous reaction motive force for subsequent suspension reactions.

[0034] Step S2, Suspension Crystallization Reaction: The premixed wastewater is pumped by lift pump 3 at a speed of 2 m 3A flow rate of [flow rate] / h is pumped into the water distribution pipe 503 at the bottom of the suspended mixing reaction tank 4. Wastewater is evenly sprayed out from the water distribution hole 502 and flows upward. At the same time, the mixing blower 7 is started to supply air to the mixing aeration system 6 at the bottom of the tank, and the aeration rate is controlled to maintain the air-to-water volume ratio at 20:1. The air rises in the form of tiny bubbles, and in the area of ​​the inclined baffle plate 501 of the inclined plate water distributor 5, the rising water flow collides, cuts, and mixes violently with the dense bubble flow. This intense air-water mixing creates excellent mass transfer conditions and ensures that the microcrystal nuclei and reaction products (mainly the target product magnesium ammonium phosphate, i.e., struvite MgNH4PO4·6H2O, and some calcium phosphate, etc.) formed in the wastewater remain in a suspended fluidized state, rather than rapidly settling. The upward flow velocity of the water is controlled at 5 m / h. Under these conditions, the microcrystal nuclei grow continuously through collision, aggregation, and surface deposition, forming larger and denser crystalline particles. A clear suspended sludge layer forms within the pool, with a stable MLSS (Mixed Lipid Saturation) of 8-12 g / L. The core innovation lies in the synergistic effect of the "5-plate inclined water distributor + bottom aeration" to create a unique "suspended crystallization" environment. The inclined plate structure achieves uniform water distribution and enhances turbulent mixing with air bubbles by altering the water flow direction. This environment achieves a dynamic balance of "reaction-crystallization-growth" within the same container, significantly increasing the contact opportunities between seed crystals and contaminants, and promoting the selective growth of high-purity, large-particle struvite crystals. Simultaneously, the suspended state allows unreacted CaO / MgO particles to continuously participate in the reaction, improving reagent utilization.

[0035] Step S3: Solid-liquid separation The large-particle suspended sludge accumulated at the bottom of the suspension reaction tank 4 is dispersed by gravity and concentration difference at a speed of approximately 0.3 m. 3 A flow rate of [amount] / h is continuously fed into the horizontal screw centrifuge 8. The centrifuge drum speed is controlled at 4200 r / min. Under the action of high centrifugal force, the heavier crystalline particles (mainly struvite) are rapidly separated to the drum wall and pushed out by the screw conveyor; the supernatant is discharged from the overflow weir at the other end. This step achieves rapid and efficient solid-liquid separation.

[0036] Step S4, Product Processing: The supernatant discharged from centrifuge 8 had the following characteristics: pH=9.2, NH3-N reduced to 35 mg / L, TP reduced to 15 mg / L, and COD reduced to 7800 mg / L. The removal rates of nitrogen and phosphorus in the supernatant reached 94.6% and 99.5%, respectively. While COD removal was limited, mainly due to the presence of recalcitrant organic matter in the wastewater, the highly efficient removal of nitrogen and phosphorus significantly reduced the load and difficulty of subsequent biological treatment. The supernatant then entered the subsequent UASB+A / O combined biological treatment system for further treatment, ultimately meeting discharge standards.

[0037] The centrifuged wet sludge (approximately 75% moisture content) is pumped to a sludge tank via sludge discharge pump 9, where it is further dehydrated by a screw press to a moisture content below 60%, yielding a grayish-white granular solid product. X-ray diffraction (XRD) analysis shows that the main component of this product is well-crystallized struvite (MgNH4PO4·6H2O), with small amounts of hydroxyapatite and calcium carbonate. Testing revealed that its total nutrient (N+P2O5) content is ≥25%, and its heavy metal content is far below the pollutant control standards for agricultural sludge. This product can be used directly or after further aging and granulation as a high-quality slow-release phosphate fertilizer or soil conditioner, achieving resource utilization of waste.

[0038] Example 2: Parameter optimization under different water quality conditions Wastewater from another activated carbon plant was treated, with slightly different water quality: pH=3.0, NH3-N=480 mg / L, TP=2800 mg / L, TDS=38000 mg / L.

[0039] The processing steps are as follows: Step s1: Adjust the mass ratio of CaO / MgO in the mixed reagent to 5:1, and the slurry concentration to 12%. The HRT in the premixing tank is 40 minutes, and the pH at the reaction endpoint is controlled to be 9.8. In step s2, in the suspended mixing reactor 4, the air-to-water ratio is controlled at 15:1, and the upward flow velocity is 4 m / h. This parameter slightly reduces the aeration intensity to accommodate a slightly lower pollutant load while still maintaining a good suspended mixing state. Step s3: Set the speed of centrifuge 8 to 3800 r / min; Step s4: After treatment, the supernatant has NH3-N < 30 mg / L and TP < 20 mg / L. The properties of the sludge product are similar to those in Example 1.

[0040] Comparative example: Traditional "lime coagulation and sedimentation + biochemical" process Wastewater from the same source as in Example 1 was treated using a traditional process: First, lime slurry (Ca(OH)2) was added to pH 11 for coagulation and sedimentation to remove most of the phosphorus (the precipitate was amorphous calcium phosphate). After sedimentation, magnesium chloride and sodium phosphate were added to the supernatant (to replenish phosphorus, as most of it had already been removed by sedimentation) for struvite precipitation to remove ammonia nitrogen, followed by another sedimentation. The effluent after these two stages of sedimentation entered the A / O biological treatment system. Results showed that: Process and footprint: The process has many units (two-stage reaction tank, two-stage sedimentation tank, biochemical tank, and secondary sedimentation tank), and the footprint is more than 2.5 times that of the process in Example 1 of this invention.

[0041] Operational stability: High salt content (TDS>40000 mg / L) severely inhibits the activity of nitrifying bacteria in the A / O system, resulting in large fluctuations in ammonia nitrogen removal rate (50%-80%), requiring frequent system adjustments and causing operational instability.

[0042] Treatment results: The final effluent ammonia nitrogen level often fluctuates between 80-150 mg / L, making it difficult to consistently meet standards. Total phosphorus can be <0.5 mg / L.

[0043] Cost and Resource Utilization: The process involves consuming a wide variety of chemicals (lime, magnesium chloride, sodium phosphate, carbon sources, etc.), resulting in high operating costs. The generated sludge is a complex mixture of phosphorus-containing chemical sludge and biological sludge, with low resource utilization value. It must be treated as hazardous waste, incurring high disposal costs.

[0044] As can be seen from the above embodiments and comparative examples, the present invention has the following significant advantages: The process is compact and requires little space: the traditional multi-step reaction precipitation is integrated into a one-step core reaction of "premixing-suspension crystallization", and with efficient centrifugal separation, the system footprint is reduced by more than 60%.

[0045] Strong resistance to shock loads and stable operation: The entire process is physical and chemical treatment, completely unaffected by the effects of high salinity and highly toxic organic matter on microorganisms, and the nitrogen and phosphorus concentrations in the effluent are stable and controllable.

[0046] Simultaneous and efficient nitrogen and phosphorus removal: Through the combination of CaO / MgO reagents and suspension crystallization process, efficient and simultaneous removal of ammonia nitrogen and phosphate is achieved in a single reactor (removal rate >94%), creating favorable conditions for subsequent biochemical treatment.

[0047] Achieving resource recovery and reducing treatment costs: Pollutants are converted into high-purity struvite fertilizer, making the resource-based product economically valuable. The dosage is customized (using inexpensive industrial-grade calcium oxide and magnesium oxide), and the suspension process improves reagent utilization. The costs of aeration, carbon source, and sludge disposal in the biological system are eliminated, resulting in an overall treatment cost reduction of approximately 30-40% compared to traditional processes.

[0048] The innovative effect of "suspension crystallization": The synergistic design of the inclined plate water distributor 5 and aeration is the key to this invention. It is not only a mixing device, but also a "crystallizer". The dynamic suspension environment it creates is a necessary condition for the formation of high-quality, easily separable crystallized products, which cannot be achieved by conventional stirred reactions or sedimentation tanks.

[0049] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention, all of which fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for nitrogen and phosphorus recovery treatment of activated carbon preparation wastewater, characterized in that, The method comprises the following steps: Step S1, pre-mixing reaction: introducing the wastewater generated by the activated carbon phosphoric acid activation method into a pre-mixing tank (1), adding a mixed reagent of calcium oxide and magnesium oxide to the wastewater, and pre-reacting under stirring for more than 30 minutes; Step S2, suspension mixing and crystallization reaction: pumping the pre-reacted wastewater into a suspension mixing reaction tank (4), the wastewater flows uniformly upward from the bottom of the suspension mixing reaction tank (4) through a inclined plate water distributor (5), and air is introduced into the bottom of the suspension mixing reaction tank (4) for aeration, the gas-water volume ratio is controlled to be 10:1-30:1, the upward flow rate of the wastewater after flowing through the area of the inclined plate water distributor (5) is controlled to be 3-7 m / h, the nitrogen and phosphorus-containing crystalline particles formed in the wastewater are kept in a suspended state in the suspension mixing reaction tank (4) to form a suspension slurry layer; Step S3, solid-liquid separation: discharging the suspension slurry from the bottom of the suspension mixing reaction tank (4) and sending it into a centrifugal separator (8) for solid-liquid separation; Step S4, product disposal: collecting the supernatant and sludge separated by the centrifugal separator (8), the supernatant enters a subsequent treatment unit, and the sludge is dewatered and used as a soil conditioner or a phosphorus fertilizer resource.

2. The method according to claim 1, wherein the method is characterized by, In step S1, the mass ratio of calcium oxide to magnesium oxide in the mixed reagent of calcium oxide and magnesium oxide is 3:1-12:

1.

3. The method according to claim 1, wherein the method is characterized by, In step S1, the mixed reagent of calcium oxide and magnesium oxide is added in the form of a slurry with a mass concentration of 10%-20%.

4. The method according to claim 1, wherein the method is characterized by, In step S2, the inclined plate water distributor (5) comprises (503) and at least one group of inclined water baffles (501) arranged above the (503), a plurality of water distribution holes (502) are formed in the water baffles (501), the wastewater is distributed through the (503) and then flows out through the water distribution holes (502) in the water baffles (501), and the wastewater collides and mixes with the upward aeration gas flow in the inclined plate area of the water baffles (501).

5. The method according to claim 1, wherein the method is characterized by, In step S3, the rotation speed of the centrifugal separator (8) during solid-liquid separation is 3000-6000 r / min.

6. A wastewater nitrogen and phosphorus recovery treatment device based on the activated carbon preparation method according to any one of claims 1-5, characterized in that, It comprises: a pre-mixing tank (1) provided with a dosing system and a stirrer (2) for pre-mixing reaction; a suspension mixing reaction tank (4) connected with the pre-mixing tank (1) through a lifting pump (3), wherein a inclined plate water distributor (5), a mixed aeration system (6) and a water outlet weir are arranged in the suspension mixing reaction tank (4) from bottom to top, the suspension mixing reaction tank (4) is used for suspension mixing and crystallization reaction, one end of the mixed aeration system (6) extends to the outside of the suspension mixing reaction tank (4) and is connected with a mixed air blower (7); a centrifugal separator (8) with its feed inlet connected with the bottom sludge discharge port of the suspension mixing reaction tank (4) for solid-liquid separation, and a sludge discharge pump (9) connected between the centrifugal separator (8) and a sludge tank; a sludge tank connected with the cake outlet of the centrifugal separator (8) for receiving and disposing the dewatered sludge.

7. The device for recovering and treating wastewater nitrogen and phosphorus by activated carbon according to claim 6, characterized in that, The water distribution device (5) comprises (503) and at least one set of water baffle plates (501) arranged obliquely above the (503), and a plurality of water distribution holes (502) are formed in the water baffle plates (501).

8. The device for recovering and treating wastewater nitrogen and phosphorus by using activated carbon according to claim 6, characterized in that, The dosing system is used for dosing mixed medicament slurry with a mass ratio of calcium oxide to magnesium oxide being 3:1-12:

1.

9. The device for recovering and treating wastewater nitrogen and phosphorus by using activated carbon according to claim 6, characterized in that, The application of the device in treating the reaction kettle wastewater or tail gas spray wastewater generated in the phosphoric acid activation method in the activated carbon preparation process is included.

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