Water treatment system and method for realizing in-situ electrochemical denitrification and metal recovery in synchronization

Abstract

The application relates to the technical field of water treatment, and discloses a water treatment system and method for synchronously realizing in-situ electrochemical denitrification and metal recovery, wherein the output end of a raw water tank is connected to the input end of an electrochemical reactor, the overflow port of the electrochemical reactor is connected to the input end of the raw water tank, an electrochemical denitrification unit is located in the electrochemical reactor, the power supply end of a direct-current voltage stabilizing power supply is connected to the electrochemical denitrification unit, the electrochemical denitrification unit is used for electrochemical denitrification in the electrochemical reactor, one end of a filtering and metal crystallization unit is connected to the electrochemical denitrification unit, the other end is connected to the recovery end of the electrochemical reactor through a reflux pipe, and the filtering and metal crystallization unit is used for metal recovery in the electrochemical reactor; high-concentration chlorine ions in water to be treated in the raw water tank are oxidized into effective chlorine at an anode in the electrochemical reactor, and the purpose of deeply removing nitrogen by-products is achieved through an indirect oxidation process, so that the deep removal of nitrate is realized.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a water treatment system and method for simultaneously achieving in-situ electrochemical denitrification and metal recovery. Background Technology

[0002] Reverse osmosis concentrate contains high concentrations of nitrate and chloride ions. In-situ utilization of chloride ions in the water allows for the in-situ removal of nitrate ions via electrochemical methods, preventing the accumulation of byproducts. One aspect of this electrochemical method is the high chloride content in RO concentrate. - High ion concentration can promote the complete removal of nitrates; on the other hand, high ion concentration can also increase the conductivity of the solution and reduce energy consumption, thereby further improving the efficiency of the electrochemical reaction. Reverse osmosis concentrate and resin regeneration solution typically contain high concentrations of metal cations, such as the common Ca2+. + and Mg2 + Previous studies have shown that magnesium in concentrated water can be recovered as Mg(OH)₂ through the additional addition of strong alkali. During the electrochemical reaction, the OH⁻ generated at the cathode can react with Ca₂ in the circulating cooling water. + and Mg2 + The reaction produces CaCO3 and Mg(OH)2 precipitates, thereby removing hardness ions. However, the descaling efficiency is low. Currently, the main solution is to use an ion-exchange membrane to separate the cathode and anode. Although this achieves good hardness removal, long-term use leads to membrane fouling and replacement issues, which are not conducive to practical application. Meanwhile, in the electrochemical treatment of NO3... - During the process, the cathode also generates a large amount of OH. - Utilizing in-situ electrochemistry of nitrate to simultaneously achieve the deposition and recovery of metal ions in water is one way to improve the economic efficiency of the system. Summary of the Invention

[0003] In order to overcome the shortcomings of the existing technology, the present invention aims to provide a water treatment system and method for simultaneously realizing in-situ electrochemical denitrification and metal recovery, so as to solve the technical problem of how to utilize in-situ electrochemistry of nitrate to simultaneously realize the deposition and recovery of metal ions in water.

[0004] This invention is achieved through the following technical solution:

[0005] In a first aspect, the present invention provides a water treatment system that simultaneously realizes in-situ electrochemical denitrification and metal recovery, including a raw water tank, an electrochemical reactor, a DC regulated power supply, an electrochemical denitrification unit, and a filtration and metal crystallization unit;

[0006] The output end of the raw water tank is connected to the input end of the electrochemical reactor, and the overflow port of the electrochemical reactor is connected to the input end of the raw water tank.

[0007] The electrochemical denitrification unit is located inside the electrochemical reactor, and the power supply terminal of the DC regulated power supply is connected to the electrochemical denitrification unit for performing electrochemical denitrification inside the electrochemical reactor.

[0008] One end of the filtration and metal crystallization unit is connected to the electrochemical denitrification unit, and the other end is connected to the recovery end of the electrochemical reactor via a reflux pipe, for metal recovery in the electrochemical reactor.

[0009] Preferably, the electrochemical denitrification unit includes an electrochemical anode and an electrochemical porous filter cathode; the electrochemical anode is connected to the anode of a DC regulated power supply, and the electrochemical porous filter cathode is connected to the cathode of a DC regulated power supply, for the dual function of electrochemical reaction and indirect oxidation of available chlorine generated after anodic oxidation in water, thereby achieving nitrate denitrification and removal of nitrogen byproducts; one end of the filtration and metal crystallization unit is connected to the electrochemical porous filter cathode.

[0010] Furthermore, the electrochemical anode is made of Pt, IrO2, or RuO2; the structure of the electrochemical anode is a plate-like structure, a rod-like structure, or a mesh structure.

[0011] Furthermore, the electrochemical porous filter cathode is made of Cu-Zn composite material, and its structure is a cylindrical mesh structure filled with Cu-Zn composite metal filter element.

[0012] Preferably, the filtration and metal crystallization unit includes an activated carbon filter, one end of which is connected to the electrochemical denitrification unit, and the other end is returned to the recovery end connected to the electrochemical reactor. The activated carbon filter contains a plurality of activated carbon particles to intercept metal ions and form scale.

[0013] Furthermore, a cathode peristaltic pump is provided between the activated carbon filter and the electrochemical denitrification unit to pump the alkaline solution in the interlayer of the electrochemical denitrification unit into the activated carbon filter for crystallization filtration.

[0014] Furthermore, the activated carbon filter is also equipped with an outlet end, at which a total nitrogen detector is installed.

[0015] Secondly, the present invention provides a water treatment method for simultaneously realizing in-situ electrochemical denitrification and metal recovery, based on the aforementioned water treatment system for simultaneously realizing in-situ electrochemical denitrification and metal recovery, comprising the following processes:

[0016] The water to be treated enters the electrochemical reactor from the raw water tank at a constant flow rate. The DC regulated power supply is started, and under the action of electrical energy, the electrochemical anode and the electrochemical porous filter cathode remove nitrate from the water to be treated in the electrochemical reactor. The overflow liquid generated after the nitrate removal is recycled to the raw water tank for repeated treatment. At the same time, the high-concentration hydroxide solution generated after the nitrate removal is sent to the activated carbon filter for crystallization filtration. Metal ion deposits are intercepted in the activated carbon filter, and the filtrate in the activated carbon filter is returned to the electrochemical reactor.

[0017] Preferably, the specific process of removing nitrate from the water to be treated by the electrochemical anode and the electrochemical porous filter cathode in the electrochemical reactor is as follows:

[0018] Under the influence of electrical energy, nitrate ions in the water to be treated are adsorbed onto the surface of the cathode of the electrochemical porous filter element, and then the copper inside the cathode of the electrochemical porous filter element reduces the nitrate ions to NH4. + -N, NO2 - -N and N2, and hydrogen gas is generated during the reduction process by electrolysis of water. The hydrogen gas escapes in the form of bubbles on the cathode surface of the electrochemical porous filter element.

[0019] Chloride ions in the water to be treated are oxidized to Cl2 at the electrochemical anode, thus forming a mixture containing HClO and ClO. - Available chlorine, available chlorine and NH4 + -N, NO2 - Indirect oxidation by -N and N2 to remove NH4 + N and NO2N form NO3. - N and N2 are used to remove nitrate ions.

[0020] Preferably, the high-concentration hydroxide solution is delivered to the activated carbon filter for crystallization filtration via a cathode peristaltic pump. The activated carbon filter intercepts metal ion deposits in the high-concentration hydroxide solution, and the total nitrogen concentration in the activated carbon filter is monitored by a total nitrogen detector. When the total nitrogen concentration in the activated carbon filter exceeds a set threshold, the reflux pipeline of the activated carbon filter is activated to return the filtrate to the electrochemical reactor for treatment.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] This invention provides a water treatment system that simultaneously achieves in-situ electrochemical denitrification and metal recovery. The output of the raw water tank is connected to the input of an electrochemical reactor, and the overflow port of the electrochemical reactor is also connected to the input of the raw water tank. An electrochemical denitrification unit is located inside the electrochemical reactor. A DC regulated power supply is connected to the electrochemical denitrification unit for electrochemical denitrification within the reactor. One end of a filtration and metal crystallization unit is connected to the electrochemical denitrification unit, and the other end is connected to the recovery end of the electrochemical reactor via a return pipe for metal recovery within the reactor. The system achieves deep removal of nitrogen byproducts by indirect oxidation of the high-concentration chloride ions in the raw water tank at the anode, resulting in effective chlorine removal. Simultaneously, the filtration and metal crystallization unit increases the homogeneous precipitation rate of magnesium hydroxide, enabling simultaneous metal ion recovery.

[0023] Furthermore, the electrochemical anode is connected to the anode of the DC regulated power supply, and the electrochemical porous filter cathode is connected to the cathode of the DC regulated power supply. Through electrochemical reactions, nitrate ions are reduced and chloride ions are oxidized, and the driving force for the reaction between chloride ion oxidation products and nitrate ion reduction products is provided, thereby achieving the purpose of in-situ treatment of chloride ions and nitrate ions.

[0024] Furthermore, the electrochemical anode is made of Pt, IrO2, or RuO2; the structure of the electrochemical anode is a plate-like structure, a rod-like structure, or a network structure, which can effectively provide the driving force for the reaction between chloride ion oxidation products and nitrate ion reduction products.

[0025] Furthermore, the electrochemical porous filter cathode is made of Cu-Zn composite material, and its structure is a cylindrical mesh structure filled with Cu-Zn composite metal filter element, which increases the contact area between the cathode and water and improves the reaction efficiency.

[0026] Furthermore, the filtration and metal crystallization unit includes an activated carbon filter. One end of the activated carbon filter is connected to the electrochemical denitrification unit, and the other end is returned to the recovery end connected to the electrochemical reactor. The activated carbon filter contains several activated carbon particles to intercept metal ions and form scale, facilitating the recovery of metal ions, improving the removal efficiency of calcium hardness, and intercepting most of the magnesium hardness deposits, providing a large number of deposition sites for calcium and magnesium hardness, greatly reducing the homogeneous sedimentation time. At the same time, the activated carbon has the ability to adsorb chlorine byproducts, effectively ensuring the quality of the effluent.

[0027] Furthermore, a cathode peristaltic pump is installed between the activated carbon filter and the electrochemical denitrification unit to pump the alkaline solution from the interlayer of the electrochemical denitrification unit into the activated carbon filter for crystallization filtration. This improves the activated carbon filter's ability to filter metal ions and allows for the extraction of the cathode alkaline solution by pumping. This avoids the problems of high cost and easy contamination associated with the previous use of ion exchange membranes and other isolation membranes, thus improving the system's economic efficiency.

[0028] Furthermore, the activated carbon filter is also equipped with an outlet end, where a total nitrogen detector is installed to facilitate monitoring of the total nitrogen concentration inside the activated carbon filter.

[0029] This invention also provides a water treatment method that simultaneously achieves in-situ electrochemical denitrification and metal recovery. By coupling in-situ electrochemical denitrification with membrane-free metal ion deposition and separation, chloride ions and nitrate ions in water can be utilized simultaneously and efficiently, realizing the related reactions between the products at each stage to achieve the purpose of denitrification. At the same time, the strongly alkaline solution generated by the cathode is recovered, and magnesium hydroxide deposits are recovered through filtration and crystallization. This method achieves nitrate denitrification and metal resource recovery simultaneously at a lower cost, providing a new coupled treatment process. This invention sets up a method for re-treatment of the overflow water from the electrochemical reactor and recirculation of unqualified product water from the activated carbon filter, ensuring the reliability of the system's effluent. It is suitable for water bodies containing high concentrations of chloride ions and nitrate ions, such as reverse osmosis concentrate and resin regeneration liquid, and has good economic benefits. Attached Figure Description

[0030] Figure 1 This is a structural diagram of the water treatment system in this invention that simultaneously achieves in-situ electrochemical denitrification and metal recovery;

[0031] In the diagram: 1-raw water tank; 2-electrochemical reactor; 3-electrochemical anode; 4-electrochemical porous filter cathode; 5-DC regulated power supply; 6-cathode peristaltic pump; 7-activated carbon filter; 8-total nitrogen analyzer. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present invention, 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0033] The present invention will now be described in further detail with reference to the accompanying drawings:

[0034] The purpose of this invention is to provide a water treatment system and method that simultaneously achieves in-situ electrochemical denitrification and metal recovery, in order to solve the technical problem of how to utilize in-situ electrochemistry of nitrate to simultaneously achieve the deposition and recovery of metal ions in water.

[0035] Example 1

[0036] See Figure 1 In one embodiment of the present invention, a water treatment system for simultaneously realizing in-situ electrochemical denitrification and metal recovery is provided, including a raw water tank 1, an electrochemical reactor 2, a DC regulated power supply 5, an electrochemical denitrification unit, and a filtration and metal crystallization unit;

[0037] The output end of the raw water tank 1 is connected to the input end of the electrochemical reactor 2, and the overflow port of the electrochemical reactor 2 is connected to the input end of the raw water tank 1.

[0038] The electrochemical denitrification unit is located inside the electrochemical reactor 2, and the power supply terminal of the DC regulated power supply 5 is connected to the electrochemical denitrification unit for electrochemical denitrification inside the electrochemical reactor 2.

[0039] One end of the filtration and metal crystallization unit is connected to the electrochemical denitrification unit, and the other end is connected to the recovery end of the electrochemical reactor 2 through a reflux pipe for metal recovery in the electrochemical reactor 2.

[0040] Specifically, the electrochemical denitrification unit includes an electrochemical anode 3 and an electrochemical porous filter cathode 4; the electrochemical anode 3 is connected to the anode of the DC regulated power supply 5, and the electrochemical porous filter cathode 4 is connected to the cathode of the DC regulated power supply 5, which is used for the dual function of electrochemical reaction and indirect oxidation of available chlorine generated after anodic oxidation in water, so as to realize nitrate denitrification and removal of nitrogen by-products; one end of the filtration and metal crystallization unit is connected to the electrochemical porous filter cathode 4.

[0041] The electrochemical anode 3 is made of Pt, IrO2 or RuO2; the structure of the electrochemical anode 3 is a plate structure, rod structure or mesh structure, and it is polished, washed with water and dried before use.

[0042] Among them, the material of the electrochemical porous filter cathode 4 is Cu-Zn composite material. The structure of the electrochemical porous filter cathode 4 is a cylindrical mesh structure, which is filled with Cu-Zn composite metal filter element with a particle size of 100-200mm.

[0043] Specifically, the filtration and metal crystallization unit includes an activated carbon filter 7. One end of the activated carbon filter 7 is connected to the electrochemical denitrification unit, and the other end is returned to the recovery end connected to the electrochemical reactor 2. The activated carbon filter 7 contains a number of activated carbons to intercept metal ions into scale, providing a large number of deposition sites for calcium carbonate and magnesium hydroxide. Calcium ions, magnesium ions, and hydroxide ions in the pumped water form homogeneous precipitates in the filter.

[0044] The activated carbon filter 7 is connected to the electrochemical denitrification unit by a cathode peristaltic pump 6, which is used to pump the alkaline solution from the interlayer of the electrochemical denitrification unit into the activated carbon filter 7 for crystallization filtration. This process intercepts and forms scale from metal ions such as calcium and magnesium in the water, achieving efficient and rapid removal of hardness and alkalinity, and simultaneously recovering calcium, magnesium and other metals.

[0045] The activated carbon filter 7 is also equipped with an outlet end, and a total nitrogen detector 8 is installed at the outlet end.

[0046] In this embodiment, the bottom inlet and top overflow port of the electrochemical reactor 2 are connected to the raw water tank 1. The reactor is equipped with an electrochemical anode 3 and an electrochemical porous filter cathode 4. The electrochemical anode 3 and the electrochemical porous filter cathode 4 are connected to the positive and negative terminals of the DC regulated power supply 5, respectively. The reactor achieves nitrate denitrification and nitrogen byproduct removal through the dual effects of electrochemical reaction and indirect oxidation of effective chlorine generated after anodic oxidation of chloride ions in the water. The raw water tank contains wastewater with high concentrations of chloride ions and nitrate ions, such as reverse osmosis concentrate and resin regeneration solution.

[0047] In summary, the water treatment system provided in this embodiment, which simultaneously achieves in-situ electrochemical denitrification and metal recovery, connects the output end of the raw water tank to the input end of the electrochemical reactor. The overflow port of the electrochemical reactor is also connected to the input end of the raw water tank. The electrochemical denitrification unit is located inside the electrochemical reactor. The power supply of the DC regulated power supply is connected to the electrochemical denitrification unit for electrochemical denitrification within the reactor. One end of the filtration and metal crystallization unit is connected to the electrochemical denitrification unit, and the other end is connected to the recovery end of the electrochemical reactor via a return pipe for metal recovery within the reactor. By using the high concentration of chloride ions in the raw water tank to be treated to generate effective chlorine at the anode through indirect oxidation, the system achieves deep removal of nitrogen byproducts, thus realizing deep removal of nitrate ions. Simultaneously, the filtration and metal crystallization unit increases the homogeneous precipitation rate of magnesium hydroxide, achieving simultaneous recovery of metal ions.

[0048] Example 2

[0049] This embodiment also provides a water treatment method for simultaneously achieving in-situ electrochemical denitrification and metal recovery. Based on the aforementioned water treatment system for simultaneously achieving in-situ electrochemical denitrification and metal recovery, the method includes the following processes:

[0050] The water to be treated enters the electrochemical reactor 2 from the raw water tank 1 at a constant flow rate. The DC regulated power supply 5 is started, and under the action of electrical energy, the electrochemical anode 3 and the electrochemical porous filter cathode 4 remove nitrate from the water to be treated in the electrochemical reactor 2. The overflow liquid generated after the nitrate removal is recycled to the raw water tank 1 for repeated treatment. At the same time, the high-concentration hydroxide solution generated after the nitrate removal is transported to the activated carbon filter 7 for crystallization filtration. Metal ion deposits are intercepted in the activated carbon filter 7, and the filtrate in the activated carbon filter 7 is returned to the electrochemical reactor 2.

[0051] Specifically, the process of removing nitrate from the water to be treated by the electrochemical anode 3 and the electrochemical porous filter cathode 4 within the electrochemical reactor 2 is as follows:

[0052] Under the action of electrical energy, nitrate ions in the water to be treated are adsorbed on the surface of the electrochemical porous filter cathode 4, and the copper inside the electrochemical porous filter cathode 4 reduces the nitrate ions to NH4. + N, NO2 - -N and N2, and hydrogen gas is generated during the reduction process by electrolysis of water. The hydrogen gas escapes in the form of bubbles on the surface of the cathode 4 of the electrochemical porous filter element.

[0053] Chloride ions in the water to be treated are oxidized to Cl2 in electrochemical anode 3, thereby forming a solution containing HClO and ClO. - Available chlorine, available chlorine and NH4 + -N, NO2 - Indirect oxidation by -N and N2 to remove NH4 + -N and NO2-N combine to form NO3- - -N and N2 are used to remove nitrate ions.

[0054] Specifically, a high-concentration hydroxide solution is transported to an activated carbon filter 7 via a cathode peristaltic pump 6 for crystallization filtration. The activated carbon filter 7 intercepts metal ion deposits in the high-concentration hydroxide solution, and the total nitrogen concentration in the activated carbon filter 7 is monitored by a total nitrogen detector 8. When the total nitrogen concentration in the activated carbon filter 7 exceeds a set threshold, the reflux pipe of the activated carbon filter 7 is activated to return the filtrate to the electrochemical reactor 2 for treatment.

[0055] In this embodiment, a cathode peristaltic pump 6 is used to draw alkaline solution from the cathode boundary layer, creating a highly alkaline Ca2+ environment in the cathode region. + Tendency to and CO32 - The formation of stable calcite crystals is achieved, and under extremely alkaline conditions at the cathode surface, aragonite and aragonite also rapidly transform into calcite. Homogeneous precipitation and filtration crystallization are relatively slow processes, which allows for the formation of looser, irregular aragonite crystals between ions, and may inhibit the transformation of aragonite to calcite. At this point, Mg2+... + Adsorbed on the surface of aragonite crystals, it prevents the rearrangement of the crystal structure. Most of the calcium hardness can be removed at the cathode, while most of the magnesium hardness is removed in homogeneous precipitation or filtration crystallization systems.

[0056] In summary, this embodiment provides a water treatment method that simultaneously achieves in-situ electrochemical denitrification and metal recovery. By coupling in-situ electrochemical denitrification with membrane-free metal ion deposition and separation, chloride ions and nitrate ions in water can be utilized simultaneously and efficiently, realizing the relevant reactions between the products at each stage to achieve the purpose of denitrification. At the same time, the strongly alkaline solution generated by the cathode is recovered, and magnesium hydroxide deposits are recovered through filtration and crystallization. This method achieves nitrate denitrification and metal resource recovery simultaneously at a lower cost, providing a new coupled treatment process. This invention sets up a method for re-treatment of the overflow water from the electrochemical reactor and recirculation of unqualified product water from the activated carbon filter, ensuring the reliability of the system's effluent. It is suitable for water bodies containing high concentrations of chloride ions and nitrate ions, such as reverse osmosis concentrate and resin regeneration liquid, and has good economic benefits.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A water treatment system that simultaneously achieves in-situ electrochemical denitrification and metal recovery, characterized in that, Includes raw water tank (1), electrochemical reactor (2), DC regulated power supply (5), electrochemical denitrification unit and filtration and metal crystallization unit; The output end of the raw water tank (1) is connected to the input end of the electrochemical reactor (2), and the overflow port of the electrochemical reactor (2) is connected to the input end of the raw water tank (1); The electrochemical denitrification unit is located inside the electrochemical reactor (2), and the power supply terminal of the DC regulated power supply (5) is connected to the electrochemical denitrification unit for electrochemical denitrification inside the electrochemical reactor (2). One end of the filtration and metal crystallization unit is connected to the electrochemical denitrification unit, and the other end is connected to the recovery end of the electrochemical reactor (2) through a reflux pipe for metal recovery in the electrochemical reactor (2). The electrochemical denitrification unit includes an electrochemical anode (3) and an electrochemical porous filter cathode (4); the electrochemical anode (3) is connected to the anode of a DC regulated power supply (5), and the electrochemical porous filter cathode (4) is connected to the cathode of a DC regulated power supply (5). It is used for the dual functions of electrochemical reaction and indirect oxidation of effective chlorine generated after anodic oxidation of chloride ions in water, to carry out nitrate denitrification and nitrogen byproduct removal; one end of the filtration and metal crystallization unit is connected to the electrochemical porous filter cathode (4); The filtration and metal crystallization unit includes an activated carbon filter (7), one end of which is connected to the electrochemical denitrification unit, and the other end is returned to the recovery end connected to the electrochemical reactor (2). The activated carbon filter (7) contains several activated carbons for intercepting metal ions to form scale.

2. The water treatment system for simultaneously realizing in-situ electrochemical denitrification and metal recovery according to claim 1, characterized in that, The electrochemical anode (3) is made of Pt, IrO2 or RuO2; the structure of the electrochemical anode (3) is a plate structure, a rod structure or a network structure.

3. The water treatment system for simultaneously realizing in-situ electrochemical denitrification and metal recovery according to claim 1, characterized in that, The electrochemical porous filter cathode (4) is made of Cu-Zn composite material. The structure of the electrochemical porous filter cathode (4) is a cylindrical mesh structure, and its interior is filled with Cu-Zn composite metal filter element.

4. A water treatment system for simultaneously realizing in-situ electrochemical denitrification and metal recovery according to claim 1, characterized in that, A cathode peristaltic pump (6) is provided between the activated carbon filter (7) and the electrochemical denitrification unit to pump the alkaline solution of the boundary layer of the electrochemical denitrification unit into the activated carbon filter (7) for crystallization filtration.

5. A water treatment system for simultaneously realizing in-situ electrochemical denitrification and metal recovery according to claim 1, characterized in that, The activated carbon filter (7) is also provided with an outlet end, and a total nitrogen detector (8) is provided at the outlet end.

6. A water treatment method for simultaneously achieving in-situ electrochemical denitrification and metal recovery, characterized in that, A water treatment system based on any one of claims 1-5, simultaneously realizing in-situ electrochemical denitrification and metal recovery, comprises the following processes: The water to be treated enters the electrochemical reactor (2) from the raw water tank (1) at a constant flow. The DC regulated power supply (5) is started. Under the action of electrical energy, the electrochemical anode (3) and the electrochemical porous filter cathode (4) remove nitrate from the water to be treated in the electrochemical reactor (2). The overflow liquid generated after the nitrate removal is recycled to the raw water tank (1) for repeated treatment. At the same time, the high-concentration hydroxide solution generated after the nitrate removal is transported to the activated carbon filter (7) for crystallization filtration. Metal ion deposits are intercepted in the activated carbon filter (7). The filtrate in the activated carbon filter (7) is returned to the electrochemical reactor (2).

7. A water treatment method for simultaneously achieving in-situ electrochemical denitrification and metal recovery according to claim 6, characterized in that, The specific process of the electrochemical anode (3) and the electrochemical porous filter cathode (4) removing nitrate from the water to be treated in the electrochemical reactor (2) is as follows: Under the action of electrical energy, nitrate ions in the water to be treated are adsorbed onto the surface of the electrochemical porous filter cathode (4), and the nitrate ions are reduced to NH4 by copper inside the electrochemical porous filter cathode (4). + -N, NO2 - -N and N2, while hydrogen gas is generated by the electrolysis of water during the reduction process. The hydrogen gas escapes in the form of bubbles on the surface of the cathode (4) of the electrochemical porous filter element. Chloride ions in the water to be treated are oxidized to Cl2 in the electrochemical anode (3), thereby forming a solution containing HClO and ClO. - Available chlorine, available chlorine and NH4 + -N, NO2 - – Indirect oxidation by N and N2 to remove NH4 + -N and NO2–N combine to form NO3. - -N and N2 are used to remove nitrate ions.

8. A water treatment method for simultaneously achieving in-situ electrochemical denitrification and metal recovery according to claim 6, characterized in that, A high-concentration hydroxide solution is transported to an activated carbon filter (7) via a cathode peristaltic pump (6) for crystallization filtration. The activated carbon filter (7) intercepts metal ion deposits in the high-concentration hydroxide solution. The total nitrogen concentration in the activated carbon filter (7) is monitored by a total nitrogen detector (8). When the total nitrogen concentration in the activated carbon filter (7) exceeds the set threshold, the return pipe of the activated carbon filter (7) is activated to return the filtrate to the electrochemical reactor (2) for treatment.

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