Electrochemical simultaneous nitrogen and phosphorus removal device and method based on bipolar membrane

Abstract

The application relates to the technical field of wastewater treatment, and discloses an electrochemical simultaneous denitrification and dephosphorization device and method based on a bipolar membrane, which comprises an electrolytic cell, a nitrate reduction cathode, an inert anode, a sacrificial anode, a nitrogen and phosphorus online monitoring sensor, a PLC controller, a water storage tank and a sedimentation tank; the inside of the electrolytic cell is divided into a left chamber and a right chamber by a bipolar membrane; the bipolar membrane is composed of a cation exchange layer and an anion exchange layer; the inert anode is arranged in the right chamber and is connected with the anode of a second direct-current power supply; the sacrificial anode is arranged in the left chamber and is connected with the anode of a first direct-current power supply. Through the double-anode structure of the inert anode and the sacrificial magnesium anode and the operation mode of step-by-step response and threshold triggering, efficient reduction of nitrate nitrogen, recycling of total phosphorus and in-situ pH regulation of the system are realized.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically to an electrochemical simultaneous nitrogen and phosphorus removal device and method based on a bipolar membrane. Background Technology

[0002] Existing methods for treating nitrate nitrogen mainly include biological denitrification, electrochemical reduction, and ion exchange. Among these, electrochemical reduction can remove NO3-. - Converted to N2 or NH4 + Phosphorus-containing wastewater is often treated using chemical precipitation methods. One such method is the crystallization and precipitation of magnesium ammonium phosphate (MgNH4PO4·6H2O) through the removal of Mg... 2+ NH4 + With PO4 3- Under suitable conditions, magnesium ammonium phosphate precipitate is formed, enabling the precipitation separation and recovery of nitrogen and phosphorus. In recent years, combining the electrochemical reduction of nitrates with the crystallization process of magnesium ammonium phosphate has attracted attention. However, within the same processing flow, it is necessary to coordinate the conversion of nitrate nitrogen, the generation of ammonium nitrogen, the supply of magnesium source, and the crystallization conditions. Existing technologies still have the following problems:

[0003] (1) Large dosage of reagent: Traditional chemical precipitation of magnesium ammonium phosphate usually requires the addition of magnesium salt to provide Mg 2+ The phosphorus is added according to the stoichiometric relationship or a certain excess coefficient based on the influent phosphorus concentration; at the same time, in order to obtain suitable crystallization conditions, alkaline agents are usually added to adjust the pH of the system. Therefore, this type of process involves the consumption of magnesium salts and acid-base adjustment agents.

[0004] (2) Reaction conditions are difficult to coordinate: NO3 - Electrochemical reduction typically requires H-rich water. + An alkaline environment is required to promote cathode electron transfer and increase the reduction rate; however, struvite precipitation requires alkaline conditions. When these two processes are carried out directly and simultaneously in the same system, their reaction environment and mass transfer conditions may affect each other, which is not conducive to the coordinated operation of nitrate nitrogen reduction and magnesium ammonium phosphate crystallization.

[0005] (3) Coupling of magnesium source release and electrochemical driving: Some existing electrochemical nitrogen and phosphorus treatment systems use magnesium anodes as both sacrificial anodes and magnesium sources, and their Mg 2+ The amount of magnesium ions released is directly related to the amount of electricity passed through, while the system current must also consider the driving demand of the electrochemical reaction. When the current density is high, the magnesium anode is consumed more quickly and surface passivation may occur; when the current density is low, the electrochemical reaction rate may be limited. Therefore, it is difficult to separately adjust the magnesium ion supply rate and the electrochemical reaction intensity in a single magnesium anode system.

[0006] (4) Mg 2+ Release and NH4 +Generation asynchrony: In traditional synchronous electrolysis systems, Mg 2+ Typically, a large amount of NO3 is released in the early stages of the reaction, and at this time... - Not yet fully converted to NH4 + , leading to Mg 2+ It cannot effectively participate in struvite formation, reducing magnesium utilization and affecting total phosphorus recovery efficiency.

[0007] In the prior art, invention patent CN118420057B discloses a method for simultaneously removing nitrogen and phosphorus and recovering struvite using electrochemical anodes and cathodes. This method employs a single-anode (e.g., magnesium plate) electrolytic cell, utilizing the corrosion of the magnesium anode to generate Mg. 2+ With PO4 in water 3- and NH4 + The reaction produces magnesium ammonium phosphate. In this type of single-anode operation, the magnesium anode serves as both the magnesium source electrode and the main power supply anode for the system. Its magnesium ion release rate is highly coupled with the current density, making independent adjustment difficult. When the current density is increased to enhance the electrochemical reaction efficiency, the magnesium anode corrodes and passivates rapidly, leading to a decrease in material utilization. The system lacks an effective pH control mechanism, making it difficult to simultaneously meet the synergistic requirements of nitrate nitrogen reduction and struvite crystallization. Utility model patent CN207158878U discloses a bioelectrochemical device for simultaneous wastewater treatment and nitrogen and phosphorus recovery. This device achieves nitrogen and phosphorus removal and partial resource recovery through bioelectrochemical methods. However, this scheme still requires the additional addition of magnesium salts for phosphorus recovery, and the pH requirements of different reaction processes still need further coordination.

[0008] In summary, existing technologies for coupling the electrochemical reduction of nitrates with the crystallization process of magnesium ammonium phosphate still face challenges such as difficulty in matching the conditions of different reaction processes, difficulty in separately adjusting the magnesium ion supply rate and the intensity of the electrochemical reaction, and the need to address the issues related to Mg. 2+ Release and NH4 + The existing electrochemical nitrogen and phosphorus co-processing devices and their operating methods still have room for improvement due to issues such as difficulty in matching the generation timing and the need for external magnesium salts or acid-base adjustment agents in some processes. Summary of the Invention

[0009] In view of this, the present invention provides a dual-anode synergistic electrochemical system based on a bipolar membrane (BPM). Through a dual-anode structure consisting of an inert anode and a sacrificial magnesium anode, and a stepwise response and threshold triggering operating mode, it achieves efficient reduction of nitrate nitrogen, resource recovery of phosphate, and in-situ pH control of the system. Compared with the traditional chemical dosing struvite method, the present invention utilizes Mg... 2+ Released in situ from the electrochemical magnesium anode, rather than by an externally added magnesium salt; OH - It is generated in situ by the bipolar film, rather than by externally added NaOH; NH4 + By NO3 -The nitrogen and phosphorus are generated in situ through electrochemical reduction, rather than through direct external addition; the entire process relies on a dual-anodine coupled electrochemical reaction to achieve simultaneous resource recovery of nitrogen and phosphorus.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: An electrochemical synchronous nitrogen and phosphorus removal device based on bipolar membrane includes an electrolytic cell, a nitrate reduction cathode, an inert anode, a sacrificial anode, an online nitrogen and phosphorus monitoring sensor, a PLC controller, a water storage tank, and a sedimentation tank; The electrolytic cell is divided into a left chamber and a right chamber by a bipolar membrane, which is composed of a cation exchange layer and an anion exchange layer. An inert anode is arranged in the right chamber and is connected to the positive terminal of the second DC power supply. A sacrificial anode is arranged in the left chamber and is connected to the positive terminal of the first DC power supply. The nitrate reduction cathode is located in the right chamber and is connected to the negative terminals of both the first and second DC power supplies. The PLC controller is electrically connected to the first DC power supply, the second DC power supply, and the nitrogen and phosphorus online monitoring sensor, respectively. The water storage tank is connected to the inlet of the electrolytic cell via a water pump, and the outlet of the electrolytic cell reaction liquid is connected to the sedimentation tank; the outlet of the sedimentation tank is connected to the return pipeline via a valve, and the other end of the return pipeline is connected to the water storage tank.

[0011] Preferably, the inert anode is a ruthenium-iridium-titanium anode (Ru-Ir-Ti), the sacrificial anode is a magnesium plate, and the nitrate reduction cathode is a Cu-Zn alloy.

[0012] Preferably, an openable partition with a magnetic stirrer is provided between the electrolytic cell and the sedimentation tank.

[0013] Preferably, a sludge discharge valve is provided at the bottom of the sedimentation tank.

[0014] This invention utilizes bipolar membrane hydrolysis to generate H in situ + and OH - This achieves self-regulation of the system's acid-base environment; by utilizing an inert anode to maintain a high current density, it increases NO3 levels. - Reduction efficiency; quantitative release of Mg using a magnesium anode 2+ This avoids the need for additional magnesium salts; Mg is achieved through independent control of dual anode currents. 2+ Release and NO3 - Reduction decoupling; by first accumulating NH4 + Mg is released afterward. 2+ The timing control improves the efficiency of struvite formation and magnesium utilization; and achieves simultaneous removal and resource recovery of nitrogen and phosphorus without the need for additional acid-base regulators.

[0015] This invention also provides a dual-anodic electrochemical simultaneous nitrogen and phosphorus removal method based on a bipolar film, implemented using the above-mentioned apparatus, comprising the following steps: (1) High-efficiency reduction of ammonium: Wastewater is pumped into the right chamber by the inlet pump, and the hose connects the right chamber and the left chamber. The PLC controller starts the second DC power supply and applies current to the inert anode and cathode, while the first DC power supply remains off; the bipolar film dissociates to generate H + The cathode supplies ammonium ions to the wastewater, where nitrate nitrogen is catalytically reduced to ammonium ions, which then accumulate continuously. (2) Monitoring and triggering: The nitrogen and phosphorus online monitoring sensor monitors the ammonium and phosphate concentrations in the solution in the right chamber in real time. When the concentrations reach or exceed the preset threshold of the PLC controller, the next step is initiated. (3) Co-precipitation: The PLC controller automatically turns on the first DC power supply and applies current to the sacrificial anode, releasing Mg through oxidation and corrosion. 2+ ; Bipolar membrane dissociation simultaneously generates OH - To create an alkaline precipitation environment, Mg in the system 2+ NH4 + PO4 3- OH - A crystallization reaction occurs to generate magnesium ammonium phosphate precipitate, achieving simultaneous removal and recovery of nitrogen and phosphorus; (4) Open the openable partition, introduce the reaction liquid into the sedimentation tank, collect the precipitate after standing to obtain magnesium ammonium phosphate, and return the obtained wastewater to the storage tank through the return pipeline, mix it with the influent water and enter the electrolytic cell again.

[0016] Preferably, in step (1), the output current density of the second DC power supply is 15 mA / cm². 2 .

[0017] Preferably, the preset threshold in step (2) is: the molar ratio of ammonium concentration to phosphate concentration in the solution reaches 1:1.

[0018] Preferably, in step (3), the output current density of the first DC power supply is 2 mA / cm². 2 .

[0019] First DC power supply: 2 mA / cm 2 This is to prevent the Mg plate from being consumed too quickly; the second DC power supply is 15 mA / cm. 2 This is to ensure sufficient overpotential for electrolysis and bipolar membrane acid and alkali production.

[0020] Preferably, in step (3), after the first DC power supply is turned on, the second DC power supply remains unchanged or the current is reduced.

[0021] The present invention also provides the application of the above-mentioned device in the treatment of nitrogen- and phosphorus-containing wastewater.

[0022] The specific reaction of this invention is as follows: Cathode nitrate reduction reaction: NO3 + 10H + + 8e → NH4 + + 3H2O; Magnesium anodizing reaction: Mg → Mg 2+ + 2e ; Bipolar membrane hydrolysis reaction: H₂O → H + + OH ; Struvite formation reaction: Mg 2+ + NH4 + + PO4 3 + 6H2O → MgNH4PO4·6H2O↓.

[0023] This invention is applicable to various nitrogen and phosphorus-containing wastewater treatment scenarios, including aquaculture tailwater, high-nitrogen and high-phosphorus industrial wastewater, anaerobic digestion liquid, landfill leachate, and agricultural wastewater.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) High nitrogen and phosphorus recovery efficiency: The pollutant nitrate nitrogen is converted into resource-recoverable ammonia nitrogen, and the total phosphorus is finally recovered in the form of struvite fertilizer, realizing the treatment of waste with waste. The sacrificial anode and the inert anode are combined in the same system and different current densities are controlled respectively, realizing the decoupled control of magnesium source addition and electrochemical reaction driving force.

[0025] (2) Low operating cost and environmentally friendly: No need to purchase magnesium salts, the slow release of Mg is controlled by low current, and the utilization rate is high; no need to add acid or alkali to adjust pH, relying on bipolar membrane water dissociation, H on one side + This promotes the reduction of nitrate nitrogen at the Cu-Zn cathode, while OH on the other side... - It provides alkalinity for struvite sedimentation without causing secondary pollution.

[0026] (3) High reaction efficiency: The high catalytic activity of Cu-Zn alloy combined with the local acidic environment (H2O) provided by the bipolar membrane + The Ru-Ir-Ti anode significantly improves the reduction rate of nitrate nitrogen; at the same time, it ensures the system stability under high current density.

[0027] (4) High controllability: Through step-by-step response and threshold triggering operation modes, the problem of Mg being released simultaneously upon startup of traditional electrolytic cells is solved. 2+ And reduced nitrate, leading to initial NH4 + Insufficient Mg 2+The problem of excessive amounts. By controlling the timing of reducing nitrogen accumulation first, followed by magnesium release and phosphorus precipitation, the utilization rate of the magnesium anode and the purity of the struvite are maximized. By adjusting the current density of the left and right anode zones separately, the generation rate of magnesium ions and the rate of pH change can be precisely balanced to adapt to different concentrations of influent water quality. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0029] Figure 1 This refers to the changes in water quality indicators in Example 1; Figure 2 Example 2 shows a comparison of removal rates under different operating modes; Figure 3 Example 2 compares magnesium utilization and energy consumption under different operating modes; Figure 4 The nitrogen and phosphorus removal effect after five cycles in Example 3; Figure 5 Example 3: magnesium anode loss and energy consumption after five cycles; Figure 6 This is an overall schematic diagram of the device of the present invention; Figure 7 This is a top view of the device of the present invention; Wherein: 1-PLC controller, 2-first DC power supply, 3-second DC power supply, 4-sacrificial anode, 5-nitrate reduction cathode, 6-inert anode, 7-nitrogen and phosphorus online monitoring sensor, 8-electrolytic cell, 9-water storage tank, 10-openable partition, 11-magnetic stirrer, 12-inlet pump, 13-valve one, 14-sedimentation tank, 15-sludge discharge valve, 16-valve two; Detailed Implementation The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] An electrochemical synchronous nitrogen and phosphorus removal device based on bipolar membrane includes an electrolytic cell 8, a nitrate reduction cathode 5, an inert anode 6, a sacrificial anode 4, a nitrogen and phosphorus online monitoring sensor 7, a PLC controller 1, a water storage tank 9, and a sedimentation tank 14. The electrolytic cell 8 is divided into a left chamber and a right chamber by a bipolar membrane, which is composed of a cation exchange layer and an anion exchange layer. An inert anode 6 is arranged in the right chamber and is connected to the positive terminal of the second DC power supply 3. A sacrificial anode 4 is arranged in the left chamber and is connected to the positive terminal of the first DC power supply 2. The nitrate reduction cathode 5 is located in the right chamber and is connected to the negative terminals of the first DC power supply 2 and the second DC power supply 3. The PLC controller 1 is electrically connected to the first DC power supply 2, the second DC power supply 3, and the nitrogen and phosphorus online monitoring sensor 7, respectively. The water storage tank 9 is connected to the inlet of the electrolytic cell 8 via the water inlet pump 12, and the reaction liquid outlet of the electrolytic cell 8 is connected to the sedimentation tank 14; the outlet of the sedimentation tank 14 is connected to the return pipeline via valve 16, and the other end of the return pipeline is connected to the water storage tank 9. The inert anode 6 is a ruthenium-iridium-titanium anode (Ru-Ir-Ti), the sacrificial anode 4 is a magnesium plate, and the nitrate reduction cathode 5 is a Cu-Zn alloy; An openable partition 10 with a magnetic stirrer 11 is provided between the electrolytic cell 8 and the sedimentation tank 14. A sludge discharge valve 15 is installed at the bottom of the sedimentation tank 14.

[0031] A dual-anodic electrochemical simultaneous nitrogen and phosphorus removal method based on a bipolar membrane, implemented using the aforementioned apparatus, includes the following steps: (1) High-efficiency reduction of ammonium: Wastewater is pumped into the right chamber by the inlet pump, and the hose connects the right chamber and the left chamber. The PLC controller starts the second DC power supply and applies current to the inert anode and cathode, while the first DC power supply remains off; the bipolar film dissociates to generate H + The cathode supplies ammonium ions to the wastewater, where nitrate nitrogen is catalytically reduced to ammonium ions, which then accumulate continuously. (2) Monitoring and triggering: The nitrogen and phosphorus online monitoring sensor monitors the ammonium and phosphate concentrations in the solution in the right chamber in real time. When the concentrations reach or exceed the preset threshold of the PLC controller, the next step is initiated. (3) Co-precipitation: The PLC controller automatically turns on the first DC power supply and applies current to the sacrificial anode, releasing Mg through oxidation and corrosion. 2+ ; Bipolar membrane dissociation simultaneously generates OH - To create an alkaline precipitation environment, Mg in the system 2+ NH4 + PO4 3- OH - A crystallization reaction occurs to generate magnesium ammonium phosphate precipitate, achieving simultaneous removal and recovery of nitrogen and phosphorus; (4) Open the openable partition, introduce the reaction liquid into the sedimentation tank, collect the precipitate after standing to obtain magnesium ammonium phosphate, and return the obtained wastewater to the storage tank through the return pipeline, mix it with the influent and then enter the electrolytic cell again. In step (1), the output current density of the second DC power supply is 15 mA / cm². 2 ; The preset threshold mentioned in step (2) is: the molar ratio of ammonium concentration to phosphate concentration in the solution reaches 1:1; In step (3), the output current density of the first DC power supply is 2 mA / cm². 2 ; In step (3), after the first DC power supply is turned on, the second DC power supply remains unchanged or the current is reduced.

[0032] Example 1: Dual-Anode Step-by-Step Batch Processing Test use Figure 6 and Figure 7 The apparatus shown is used for batch processing. In this embodiment, a bipolar membrane manufactured by Jiangsu Lanbo New Material Technology Co., Ltd. is employed. The effective volume of the electrolytic cell is 2.0 L, and the effective areas of the Ru-Ir-Ti anode, magnesium plate anode, and Cu-Zn alloy cathode are all 100 cm². 2 The electrode spacing is 30 mm, and the effective area of ​​the bipolar film is 80 cm². 2 The magnetic stirring speed was 300 r / min, and the reaction temperature was 25℃. The initial nitrate nitrogen concentration of the simulated wastewater was 50.2 mg / L, the phosphate concentration (as phosphorus) was 15.1 mg / L, the ammonium nitrogen concentration was 0.18 mg / L, and the initial pH was 7.12.

[0033] The first stage involves starting the second DC power supply connected to the inert anode at a current density of 15 mA / cm². 2 NO3 is carried out during this stage. - -N reduction with NH4 + -N accumulation. When NH4... + -N and PO4 3- The second stage is triggered when the molar ratio of -P reaches 1:1. This batch reached the trigger condition after 75 minutes of operation, after which the first DC power supply connected to the magnesium anode was turned on at a current density of 2 mA / cm². 2 And reduce the current density of the second DC power supply to 8 mA / cm². 2 Continue the reaction for 20 minutes. After the co-precipitation is complete, transfer the mixture to a sedimentation tank and let it stand for 30 minutes to separate the solid and liquid phases.

[0034] Based on the above data, NO3 - -N removal rate was 69.7%, inorganic nitrogen removal rate was 68.4%, PO4 removal rate was 68.4%. 3--P removal rate was 95.8%; based on the peak ammonium nitrogen level at the end of the first stage, ammonium nitrogen precipitation recovery rate was 89.6%. At 75 min, NH4... + -N and PO4 3- The molar ratio of -P is 1.03:1, and the PLC triggers the magnesium anode accordingly.

[0035] The magnesium anode experienced a mass loss of 29.0 mg in the second stage, with a theoretical dissolution rate of 30.2 mg based on electricity consumption. The magnesium entering the magnesium ammonium phosphate crystals, calculated from the total phosphorus removal, was approximately 22.7 mg, resulting in a magnesium utilization rate of approximately 78.3%. The collected and dried precipitate weighed 0.221 g, with a Mg:N:P molar ratio of 1.04:0.98:1.00. The average cell voltage in the first stage was 4.60 V, while the average cell voltages in the inert anode circuit and magnesium anode circuit in the second stage were 3.90 V and 3.20 V, respectively, translating to an energy consumption of approximately 4.94 kWh / m³. 3 .

[0036] Example 2: Comparative Test of Step-by-Step Operation and Different Operation Modes Under the same influent water quality, reaction volume, and total operating time as in Example 1, four comparative groups were set up: Group A adopted the bipolar membrane dual-anode stepwise operation mode of the present invention; Group B started the inert anode and magnesium anode simultaneously at the start of the reaction; Group C replaced the bipolar membrane with a conventional cation exchange membrane, with other conditions the same as Group A and no external acid or alkali added; Group D used only the magnesium anode and operated at 15 mA / cm². 2 Continuous operation. Simulation results for each group are shown below. Figure 2 and Figure 3 .

[0037] Depend on Figure 2 and Figure 3 It is evident that step-by-step triggering significantly reduces the ineffective dissolution of magnesium before ammonium nitrogen accumulates. Compared to the synchronous start-up group, Group A showed approximately 80% reduction in magnesium plate loss, an increase in magnesium utilization rate from 14% to 78%, and an increase in total phosphorus removal rate of approximately 8%. Compared to Group C, which used a conventional cation exchange membrane, Group A showed significantly improved removal rates for nitrate nitrogen, inorganic nitrogen, and total phosphorus, indicating that the bipolar membrane generates H2 in situ. + and OH - This facilitates the synergistic effect of nitrate nitrogen reduction and magnesium ammonium phosphate crystallization. While a single magnesium anode group can achieve a higher total phosphorus removal rate, it significantly increases magnesium plate consumption, highlighting the advantage of independent control via dual anodes.

[0038] Example 3: Reflux Cycle Stability Test Five-cycle batch tests were conducted using the operating conditions of Example 1. After each cycle, 20% of the supernatant from the sedimentation tank was recycled to the storage tank, and simulated wastewater was added to maintain the initial NO3 levels for each cycle. --N and PO4 3- -P concentrations were restored to approximately 50 mg / L and 15 mg / L, respectively. Each cycle was performed according to NH4... + -N and PO4 3- -P molar ratio reaches the threshold of 1:1 to start up magnesium anode.

[0039] PO4 in five cycles 3- -P removal rate remained above 94%, inorganic nitrogen removal rate remained above 66%, unit treatment energy consumption was low, and fluctuation range was less than 4%. These results indicate that the bipolar membrane, inert anode, and Cu-Zn cathode have good operational stability and application prospects under reflux operation conditions.

[0040] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrochemical simultaneous nitrogen and phosphorus removal device based on a bipolar membrane, characterized in that, Includes an electrolytic cell, nitrate reduction cathode, inert anode, sacrificial anode, nitrogen and phosphorus online monitoring sensors, PLC controller, water storage tank, and sedimentation tank; The electrolytic cell is divided into a left chamber and a right chamber by a bipolar membrane, which is composed of a cation exchange layer and an anion exchange layer. An inert anode is arranged in the right chamber and is connected to the positive terminal of the second DC power supply. A sacrificial anode is arranged in the left chamber and is connected to the positive terminal of the first DC power supply. The nitrate reduction cathode is located in the right chamber and is connected to the negative terminals of both the first and second DC power supplies. The PLC controller is electrically connected to the first DC power supply, the second DC power supply, and the nitrogen and phosphorus online monitoring sensor, respectively. The water storage tank is connected to the inlet of the electrolytic cell via a water pump, and the outlet of the electrolytic cell reaction liquid is connected to the sedimentation tank; the outlet of the sedimentation tank is connected to the return pipeline via a valve, and the other end of the return pipeline is connected to the water storage tank.

2. The bipolar membrane-based electrochemical simultaneous nitrogen and phosphorus removal device according to claim 1, characterized in that, The inert anode is a ruthenium-iridium-titanium anode, the sacrificial anode is a magnesium plate, and the nitrate reduction cathode is a Cu-Zn alloy.

3. The bipolar membrane-based electrochemical simultaneous nitrogen and phosphorus removal device according to claim 1, characterized in that, An openable partition with a magnetic stirrer is provided between the electrolytic cell and the sedimentation tank.

4. The bipolar membrane-based electrochemical simultaneous nitrogen and phosphorus removal device according to claim 1, characterized in that, A sludge discharge valve is installed at the bottom of the sedimentation tank.

5. A dual-anodic electrochemical simultaneous nitrogen and phosphorus removal method based on a bipolar membrane, implemented using the apparatus described in any one of claims 1-4, characterized in that, Includes the following steps: (1) High-efficiency reduction of ammonium: Wastewater is pumped into the right chamber by the inlet pump, and the hose connects the right chamber and the left chamber. The PLC controller starts the second DC power supply and applies current to the inert anode and cathode, while the first DC power supply remains off; the bipolar film dissociates to generate H + The cathode supplies ammonium ions to the wastewater, where nitrate nitrogen is catalytically reduced to ammonium ions, which then accumulate continuously. (2) Monitoring and triggering: The nitrogen and phosphorus online monitoring sensor monitors the ammonium and phosphate concentrations in the solution in the right chamber in real time. When the concentrations reach or exceed the preset threshold of the PLC controller, the next step is initiated. (3) Co-precipitation: The PLC controller automatically turns on the first DC power supply and applies current to the sacrificial anode, releasing Mg through oxidation and corrosion. 2+ ; Bipolar membrane dissociation simultaneously generates OH - To create an alkaline precipitation environment, Mg in the system 2+ NH4 + PO4 3- OH - A crystallization reaction occurs to generate magnesium ammonium phosphate precipitate, achieving simultaneous removal and recovery of nitrogen and phosphorus; (4) Open the openable partition, introduce the reaction liquid into the sedimentation tank, collect the precipitate after standing to obtain magnesium ammonium phosphate, and return the obtained wastewater to the storage tank through the return pipeline, mix it with the influent water and enter the electrolytic cell again.

6. The method for simultaneous nitrogen and phosphorus removal based on a bipolar film using dual-anodic electrochemical methods according to claim 5, characterized in that, In step (1), the output current density of the second DC power supply is 15 mA / cm². 2 .

7. The method for simultaneous nitrogen and phosphorus removal based on a bipolar film using dual-anodic electrochemical methods according to claim 5, characterized in that, The preset threshold in step (2) is: the molar ratio of ammonium concentration to phosphate concentration in the solution reaches 1:

1.

8. The method for simultaneous nitrogen and phosphorus removal based on a bipolar film using dual-anodic electrochemical methods according to claim 5, characterized in that, In step (3), the output current density of the first DC power supply is 2 mA / cm². 2 .

9. The method for simultaneous nitrogen and phosphorus removal based on a bipolar film using dual-anodic electrochemical methods according to claim 5, characterized in that, In step (3), after the first DC power supply is turned on, the second DC power supply remains unchanged or the current is reduced.

10. The application of the apparatus according to any one of claims 1-4 in the treatment of nitrogen- and phosphorus-containing wastewater.

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