A treatment system and process for efficiently removing ammonia nitrogen from low-salinity wastewater

Abstract

The present invention discloses a treatment system and process for efficiently removing ammonia nitrogen from low-salinity wastewater, which belongs to the technical field of wastewater treatment for environmental protection. The treatment system includes an electrocatalytic oxidation tank, an inlet distribution tank, an electrodialysis device, a concentrated water intermediate tank and a fresh water intermediate tank; wherein the electrocatalytic oxidation tank provides a place for ammonia nitrogen removal reaction, including a concentrated chamber, a first compartment of a fresh water chamber and a second compartment of a fresh water chamber. The process steps are as follows: after the pH of the low-salinity wastewater to be treated is adjusted in the inlet distribution tank, it enters the electrodialysis device; the concentrated water and the polar water produced by the electrodialysis are mixed and the water quality is adjusted, and then enter the concentrated chamber of the electrocatalytic oxidation tank for electrocatalytic oxidation reaction to remove ammonia nitrogen; the denitrified concentrated water is then mixed with the fresh water produced by the electrodialysis for reaction, and finally discharged together. The treatment system and process can remove ammonia nitrogen from low-salinity wastewater with low consumption and high selectivity, and the energy consumption required for unit mass ammonia nitrogen removal is saved by more than 30% compared with the conventional electrocatalytic oxidation process, and the treated water has less negative impact on the subsequent biochemical system.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and more specifically, to a treatment system and process for efficiently removing ammonia nitrogen from low-salinity wastewater. Background Art

[0002] Ammonia (NH3) is an extremely important raw material for synthetic chemical industry and is widely used in medicine, pesticides, fertilizers, petrochemicals, smelting and other industries. Due to its excellent water solubility, ammonia is inevitably present in related production wastewater and has become a target pollutant strictly controlled in the field of water pollution control - ammonia nitrogen. In addition, the decomposition of nitrogen-containing organic matter will also produce ammonia nitrogen-containing wastewater, such as food manufacturing plant wastewater, landfill leachate, etc. Electrocatalytic oxidation technology is a treatment technology that uses special catalytic electrode plates to form an electrolysis system to oxidize pollutants in wastewater. It has been successfully applied in the removal of ammonia nitrogen and organic matter. Its principle can be divided into direct oxidation and indirect oxidation: direct oxidation refers to the direct loss of electrons by pollutants at the anode plate; indirect oxidation mainly uses the loss of electrons by chloride ions in the wastewater at the anode plate to generate chlorine, hypochlorite and other active oxidizing species to oxidize pollutants in the wastewater. It has been proven to be the main way to remove ammonia nitrogen and organic matter.

[0003] The nature of electrocatalytic oxidation technology determines that the wastewater to be treated must contain a certain amount of salt to conduct current. However, some wastewater containing ammonia nitrogen has a low salt content (<1.5%), such as condensed water obtained by distilling salt from high-salt wastewater. When such low-salt wastewater enters anaerobic, aerobic and other biochemical systems, the impact caused by ammonia nitrogen is often stronger than that of organic matter, so its main removal target is ammonia nitrogen rather than organic matter. At present, electrocatalytic oxidation technology still faces the following difficulties in removing ammonia nitrogen from low-salinity wastewater: (1) The low salinity of the wastewater leads to a higher voltage required for electrocatalysis at the same current intensity, high power, high treatment cost, and serious heat generation and heat accumulation in the wastewater, which brings certain safety hazards; if salt is directly added to the wastewater to reduce the voltage, the salt content of the wastewater will increase, which is not conducive to subsequent biochemical treatment, and may cause the salt content in the final wastewater to exceed the relevant limit; (2) Ammonia nitrogen and organic matter coexist in the wastewater, but active oxidizing species such as chlorine and hypochlorite do not have the ability to selectively denitrify, resulting in some active oxidizing species oxidizing organic matter, and the oxidation removal efficiency of the target ammonia nitrogen is low; if the ammonia nitrogen is to be reduced to the treatment target, the oxidation time needs to be extended, resulting in increased energy consumption costs. Therefore, in order to solve the problem that conventional electrocatalytic oxidation technology cannot remove ammonia nitrogen from low-salinity wastewater with low consumption and high selectivity, it is necessary to propose a treatment system and process for efficiently removing ammonia nitrogen from low-salinity wastewater, so as to at least partially solve the problems existing in the prior art. Summary of the invention

[0004] A series of simplified concepts are introduced in the Summary of the Invention, which will be further described in detail in the Detailed Description of the Invention. The Summary of the Invention does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the scope of protection of the claimed technical solution.

[0005] In order to at least partially solve the above problems, the present invention provides a treatment system and process for efficiently removing ammonia nitrogen from low-salinity wastewater, comprising:

[0006] An electrocatalytic oxidation tank, an inlet distribution tank, an electrodialysis device, a concentrated water intermediate tank and a fresh water intermediate tank; the electrocatalytic oxidation tank provides a reaction site for ammonia nitrogen removal, including a concentrated chamber, a first compartment of a fresh water chamber and a second compartment of a fresh water chamber; the inlet distribution tank receives low-salt wastewater to be treated, and is connected to the water inlet of the electrodialysis device through a pump and a pipeline; the concentrated water intermediate tank receives concentrated water and polar water produced by the electrodialysis device, and is connected to the electrocatalytic oxidation tank through a pump and a pipeline; the fresh water intermediate tank receives fresh water produced by the electrodialysis device, and is connected to the electrocatalytic oxidation tank through a pump and a pipeline.

[0007] Preferably, the concentration chamber is located between the first grid of the dilute chamber and the second grid of the dilute chamber, an electrocatalytic plate group is arranged in the concentration chamber, the concentrated water intermediate tank is connected to the concentration chamber water inlet of the concentration chamber, the concentration chamber water inlet is arranged at the upper part of the concentration chamber, and the position is higher than the top of the electrocatalytic plate group; the fresh water intermediate tank is connected to the first grid water inlet of the first grid of the dilute chamber, and the first grid water inlet is arranged at the lower part of the first grid of the dilute chamber.

[0008] Preferably, the concentration chamber further comprises:

[0009] The water outlet of the concentration chamber is arranged at the lower part of the concentration chamber, connecting the concentration chamber and the first compartment of the dilution chamber;

[0010] The concentration chamber gas outlet port 1 is arranged at the upper part of the concentration chamber, connecting the concentration chamber and the gas outlet pipe 1;

[0011] The second gas outlet of the concentration chamber is arranged at the upper part of the concentration chamber and connects the concentration chamber and the second gas outlet pipe.

[0012] Preferably, the concentration chamber further comprises:

[0013] A pressure gauge is arranged at the top of the concentration chamber to monitor the gas pressure in the concentration chamber;

[0014] Liquid level meter, which is installed in the concentration chamber to monitor the wastewater level in the concentration chamber;

[0015] A mechanical stirring device is arranged in the concentration chamber to stir and mix the wastewater in the concentration chamber.

[0016] Preferably, the first compartment of the light room also includes:

[0017] Aeration system 1, aeration system 1 is connected to concentration chamber outlet 1 through outlet pipe 1;

[0018] The first water outlet is arranged at the upper part of the first water outlet of the dilute chamber and connected to the second water outlet of the dilute chamber through a pipeline;

[0019] The first air inlet is arranged at the top of the first compartment of the dilute chamber, connecting the first compartment of the dilute chamber with the outside atmosphere;

[0020] The first compartment exhaust port is arranged at the top of the first compartment of the dilute chamber and is connected to the second compartment of the dilute chamber through a pipeline.

[0021] Preferably, the second compartment of the light room also includes:

[0022] Aeration system 2, aeration system 2 is connected to concentration chamber gas outlet 2 through gas outlet pipe 2;

[0023] The second compartment water inlet is arranged at the lower part of the second compartment of the desalination chamber, and the second compartment water inlet is connected to the first compartment water outlet through a pipeline;

[0024] The second water outlet is arranged at the upper part of the second water outlet of the desalination chamber;

[0025] The second air inlet is arranged at the top of the second compartment of the dilute chamber, and the second air inlet is connected to the first air outlet through a pipeline;

[0026] The second compartment exhaust port is arranged at the top of the second compartment of the dilute chamber, and is connected to the induced draft fan through a pipeline to lead the exhaust gas generated by the entire electrocatalytic oxidation tank to the exhaust gas treatment system.

[0027] Preferably, the anode plate on the electrocatalytic plate group is set as a titanium plate coated with one or more materials of ruthenium, iridium, tantalum, and platinum, and the anode plate is connected to the positive electrode of the DC power supply; the cathode plate on the electrocatalytic plate group is set as any one of a titanium plate, a copper plate, stainless steel, and graphite, and the cathode plate is connected to the negative electrode of the DC power supply; the current density on the plate is controlled to be 100-800A / m 2 .

[0028] Preferably, the total salt content of the low-salt wastewater to be treated is less than 1.5%, the chloride ion content is less than 1.0%, and the ammonia nitrogen content is 100-4000 mg / L.

[0029] Preferably, a process using the treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater comprises the following steps:

[0030] S1: The low-salt wastewater to be treated enters the water distribution tank and is adjusted to pH 4-6 by adding hydrochloric acid or liquid alkali;

[0031] S2: The low-salt wastewater with adjusted pH in the inlet distribution tank enters the electrodialysis device, and produces fresh water, concentrated water and polar water under the action of electrodialysis, wherein the fresh water is discharged into the fresh water intermediate tank, and the concentrated water and polar water are mixed and discharged into the concentrated water intermediate tank, and the pH is adjusted to 7-10 by adding liquid alkali. If the chloride ion content of the mixed concentrated water in the concentrated water intermediate tank is lower than 1.0%, a certain amount of sodium chloride is added thereto;

[0032] S3: The mixed concentrated water with adjusted water quality in the concentrated water intermediate tank enters the concentrated chamber of the electrocatalytic oxidation tank for electrocatalytic oxidation reaction to effectively remove ammonia nitrogen, and then enters the first compartment of the dilute chamber to be mixed with the fresh water from the fresh water intermediate tank and undergo secondary oxidation reaction. The mixed wastewater in the first compartment of the dilute chamber is discharged into the second compartment of the dilute chamber for tertiary oxidation reaction and finally discharged into the subsequent treatment system through the outlet of the second compartment.

[0033] Compared with the prior art, the present invention has at least the following beneficial effects:

[0034] The present invention provides a treatment system and process for efficiently removing ammonia nitrogen from low-salinity wastewater.

[0035] (1) Through the electrodialysis device, inorganic salts and ammonia nitrogen in low-salt wastewater are removed After enriching in the concentrated water, the electrocatalytic oxidation plate group is transformed from directly treating all the low-salt wastewater to treating a small amount of concentrated water. The salinity of the wastewater is relatively high, and the required voltage is greatly reduced. It also avoids excessive heat generation and accumulation of the wastewater, and is safer. Even if salt needs to be added, it only needs to be added to the concentrated water, and the overall salt supplement amount is less, which has less impact on the subsequent biochemical stage.

[0036] (2) Compared with the original low-salt wastewater, the concentrated water obtained by the electrodialysis device has a higher ratio of ammonia nitrogen to organic matter concentration, which is beneficial to improving the subsequent electrocatalytic oxidation efficiency of ammonia nitrogen removal, with higher denitrification selectivity and shorter processing time. The energy consumption required for the removal of unit mass of ammonia nitrogen in the entire system saves more than 30% compared with the conventional electrocatalytic oxidation process.

[0037] (3) By setting up the first and second compartments of the dilute chamber, the wastewater is changed from a completely mixed state in a conventional electrocatalytic oxidation device to a plug flow state, and the residual chlorine in the final effluent is lower, which can reduce the negative impact of the residual chlorine on the subsequent biochemical process; the waste gas generated in the concentration chamber is introduced into the wastewater in the dilute chamber through the outlet pipe, so that the residual chlorine in the waste gas undergoes secondary and tertiary oxidation reactions with the pollutants in the wastewater in the dilute chamber, thereby improving the utilization efficiency of active oxidation species and reducing the burden on the waste gas treatment system.

[0038] The present invention describes a treatment system and process for efficiently removing ammonia nitrogen from low-salt wastewater. Other advantages, objectives and features of the present invention will be reflected in part through the following description, and in part will be understood by technicians in this field through research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0040] Figure 1 It is a schematic diagram of a treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater according to the present invention;

[0041] Figure 2 It is a schematic top view of the electrocatalytic oxidation tank in the treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater of the present invention.

[0042] In the figure: 1. electrocatalytic oxidation tank; 2. water inlet distribution tank; 3. electrodialysis device; 4. concentrated water intermediate tank; 5. fresh water intermediate tank; 6. first compartment water inlet; 7. aeration system one; 8. concentrated chamber water outlet; 9. electrocatalytic plate group; 10. concentrated chamber; 11. second compartment water inlet; 12. aeration system two; 13. the first compartment of the fresh chamber; 14. outlet pipe one; 15. the first compartment water outlet; 16. concentrated chamber water inlet; 17. concentrated chamber air outlet one; 18. the first compartment air inlet; 19. the first compartment air outlet; 20. pressure gauge; 21. liquid level gauge; 22. the second compartment air inlet; 23. induced draft fan; 24. the second compartment air outlet; 25. concentrated chamber air outlet two; 26. air outlet pipe two; 27. the second compartment water outlet; 28. mechanical stirring device; 29. ​​the second compartment of the fresh chamber. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments so that those skilled in the art can implement the invention with reference to the description.

[0044] It should be understood that terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0045] like Figure 1 , 2 As shown, the present invention provides a treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater, comprising:

[0046] An electrocatalytic oxidation tank 1, an inlet distribution tank 2, an electrodialysis device 3, a concentrated water intermediate tank 4 and a fresh water intermediate tank 5. The electrocatalytic oxidation tank 1 provides a reaction site for ammonia nitrogen removal, including a concentrated chamber 10, a first compartment 13 of a fresh water chamber and a second compartment 29 of a fresh water chamber; the inlet distribution tank 2 receives low-salt wastewater to be treated, and is connected to the water inlet of the electrodialysis device 3 through a pump and a pipeline; the concentrated water intermediate tank 4 receives concentrated water and polar water produced by the electrodialysis device 3, and is connected to the electrocatalytic oxidation tank 1 through a pump and a pipeline; the fresh water intermediate tank 5 receives fresh water produced by the electrodialysis device 3, and is connected to the electrocatalytic oxidation tank 1 through a pump and a pipeline.

[0047] The concentration chamber 10 is located between the first cell 13 of the dilute chamber and the second cell 29 of the dilute chamber. An electrocatalytic plate group 9 is arranged in the concentration chamber 10. The concentrated water intermediate tank 4 is connected to the concentration chamber water inlet 16 of the concentration chamber 10. The concentrated chamber water inlet 16 is arranged at the upper part of the concentration chamber 10 and is higher than the top of the electrocatalytic plate group 9; the fresh water intermediate tank 5 is connected to the first cell water inlet 6 of the first cell 13 of the dilute chamber. The first cell water inlet 6 is arranged at the lower part of the first cell 13 of the dilute chamber.

[0048] The working principle and beneficial effects of the present invention are:

[0049] The present invention provides a treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater. When used, the low-salinity wastewater to be treated is adjusted to pH 4-6 in the water inlet distribution tank 2 so that the ammonia nitrogen is uniformly distributed in the water inlet distribution tank 2. The inorganic salts and The concentrated water is then enriched in concentrated water, which then enters the concentrated chamber 10 of the electrocatalytic oxidation tank 1, where the ammonia nitrogen is oxidized into nitrogen gas mainly by the hypochlorous acid (root) produced by electrolysis of the electrocatalytic plate group 9, thereby achieving the removal of ammonia nitrogen. The denitrified concentrated water is then mixed with fresh water for secondary and tertiary oxidation reactions, and the final effluent is discharged into the subsequent biochemical section.

[0050] The power consumption of electrocatalytic oxidation process for removing ammonia nitrogen increases with the decrease of salt content in wastewater. When the salt content is less than 1.5%, the power consumption reaches 25-40kW / t wastewater. Electrodialysis is a technology that uses an external DC electric field and anion and cation selective exchange membranes to enrich inorganic salts. It has the advantages of tolerance to organic matter and stable operation. Its overall power consumption has no direct relationship with the amount of water treated, but is only proportional to the total amount of ions in the final concentrated water. When treating low-salt wastewater, the power consumption per ton of water is only 1 / 15-1 / 10 of that of electrocatalytic oxidation technology.

[0051] The present invention couples electrodialysis and electrocatalytic oxidation, and enriches inorganic salts and ammonia nitrogen in low-salt wastewater into concentrated water through electrodialysis, and changes electrocatalytic oxidation to directly treat all low-salt wastewater to treat a small part of concentrated water, which greatly reduces the required voltage, reduces energy consumption and heat generation, and even if the salt content in the concentrated water is low, only salt needs to be added to the concentrated water, and the comprehensive salt supplement amount is less, which has less impact on the subsequent biochemical process. The first compartment of the dilute chamber and the second compartment of the dilute chamber of the electrocatalytic oxidation tank are placed on both sides of the concentrated chamber, which can effectively transfer and absorb the heat released by the electrocatalytic oxidation of the concentrated chamber, avoid excessive heat accumulation of wastewater, and improve the safety of the system. Due to the barrier of organic matter by anion and cation selective exchange membranes, the concentrated water produced by electrodialysis has a higher ammonia nitrogen to organic matter concentration ratio than the original low-salt wastewater, which is conducive to improving the oxidation and removal efficiency of ammonia nitrogen by subsequent electrocatalytic oxidation, and the denitrification selectivity is higher, and the processing time can be shorter. The energy consumption required for the removal of unit mass of ammonia nitrogen in the entire system is saved by more than 30% compared with the conventional electrocatalytic oxidation process. The denitrified concentrated water is remixed with the fresh water in the first compartment of the dilute chamber, which solves the problem of concentrated water disposal. The residual chlorine in the concentrated water can undergo secondary oxidation reaction with organic matter in the fresh water and be consumed, thereby improving the utilization efficiency of active oxidation species and reducing the residual chlorine content in the effluent.

[0052] In one embodiment, the concentration chamber 10 further comprises:

[0053] The concentrated chamber water outlet 8 is arranged at the lower part of the concentrated chamber 10, connecting the concentrated chamber 10 and the first compartment 13 of the dilute chamber;

[0054] The concentration chamber gas outlet 17 is arranged at the upper part of the concentration chamber 10, connecting the concentration chamber 10 and the gas outlet pipe 14;

[0055] The second concentration chamber gas outlet 25 is disposed at the upper portion of the concentration chamber 10 and connects the concentration chamber 10 and the second gas outlet pipe 26;

[0056] A pressure gauge 20, which is disposed at the top of the concentration chamber 10 and is used to monitor the gas pressure in the concentration chamber 10;

[0057] A liquid level meter 21, which is disposed in the concentration chamber 10 and is used to monitor the wastewater level in the concentration chamber 10;

[0058] The mechanical stirring device 28 is disposed in the concentration chamber 10 and is used to stir and mix the wastewater in the concentration chamber 10 .

[0059] The working principle and beneficial effects of the above technical solution are:

[0060] By setting the concentration chamber water outlet 8, the concentration chamber gas outlet 1 17 and the concentration chamber gas outlet 2 25, the discharge of waste water and waste gas in the concentration chamber is achieved; by setting the pressure gauge 20 and the liquid level gauge 21, the gas pressure and the waste water level in the concentration chamber 10 are monitored, and an external electronic control system can be connected to dynamically adjust the exhaust rate and the water inlet rate of the concentration chamber 10 to avoid excessive gas pressure and waste water level and maintain the safety of the electrocatalytic system; by setting the mechanical stirring device 28, the rapid mixing and reaction of the concentrated water can be guided to improve the denitrification efficiency.

[0061] In one embodiment, the first compartment 13 of the dilute room further comprises:

[0062] Aeration system 7, aeration system 7 is connected to concentration chamber outlet 17 through outlet pipe 14;

[0063] The first water outlet 15 is arranged at the upper part of the first water outlet 13 of the dilute chamber and connected to the second water outlet 29 of the dilute chamber through a pipeline;

[0064] The first air inlet 18 is arranged at the top of the first compartment 13 of the dilute chamber, connecting the first compartment 13 of the dilute chamber with the outside atmosphere;

[0065] The first compartment exhaust port 19 is arranged at the top of the first compartment 13 of the dilute chamber and is connected to the second compartment 29 of the dilute chamber through a pipeline.

[0066] In one embodiment, the second compartment 29 of the dilute room further comprises:

[0067] Aeration system 2 12, aeration system 2 12 is connected to concentration chamber gas outlet 2 25 through gas outlet pipe 2 26;

[0068] The second water inlet 11 is disposed at the lower part of the second compartment 29 of the desalination chamber, and the second water inlet 11 is connected to the first water outlet 15 through a pipeline;

[0069] The second water outlet 27 is disposed at the upper portion of the second water outlet 29 of the desalination chamber;

[0070] The second air inlet 22 is arranged at the top of the second air inlet 29 of the dilute chamber, and the second air inlet 22 is connected to the first air outlet 19 through a pipeline;

[0071] The second compartment exhaust port 24 is arranged at the top of the second compartment 29 of the dilute chamber, and is connected to the induced draft fan 23 through a pipeline to lead out the exhaust gas generated by the entire electrocatalytic oxidation tank 1 to the exhaust gas treatment system.

[0072] The working principle and beneficial effects of the above technical solution are:

[0073] By setting up an aeration system 1 7 and an aeration system 2 12, the waste gas in the concentration chamber 10 is introduced into the mixed wastewater in the first compartment 13 of the dilution chamber and the second compartment 29 of the dilution chamber respectively. On the one hand, it can stir the wastewater, and on the other hand, it can make the residual chlorine in the waste gas be reabsorbed by the wastewater and then react with organic matter, thereby improving the utilization efficiency of active oxidation species and reducing the burden of the waste gas treatment system; by reasonably arranging the wastewater inlet and outlet of the first compartment 13 of the dilution chamber and the second compartment 29 of the dilution chamber, the wastewater therein can present a plug flow state rather than a completely mixed state of a conventional electrocatalytic oxidation device, and the residual chlorine in the final effluent is lower, which can reduce the negative impact of the residual chlorine on the subsequent biochemical stage.

[0074] In one embodiment, the anode plate on the electrocatalytic plate group 9 is set as a titanium plate coated with one or more materials of ruthenium, iridium, tantalum, and platinum, and the anode plate is connected to the positive electrode of the DC power supply; the cathode plate on the electrocatalytic plate group 9 is set as any one of a titanium plate, a copper plate, stainless steel, and graphite, and the cathode plate is connected to the negative electrode of the DC power supply; the current density on the plate is controlled to be 100-800A / m 2 .

[0075] In one embodiment, the total salt content of the low-salt wastewater to be treated is less than 1.5%, the chloride ion content is less than 1.0%, and the ammonia nitrogen content is 100-4000 mg / L.

[0076] The working principle and beneficial effects of the above technical solution are:

[0077] The ammonia nitrogen content of the low-salt wastewater to be treated is 100-4000 mg / L, which is consistent with the general treatment capacity of the electrocatalytic oxidation tank and provides a suitable wastewater parameter range for the treatment system provided by the present invention.

[0078] In one embodiment, a process using the treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater comprises the following steps:

[0079] S1: The low-salt wastewater to be treated enters the water distribution tank 2 and is adjusted to pH 4-6 by adding hydrochloric acid or liquid alkali;

[0080] S2: The low-salt wastewater with adjusted pH in the water inlet distribution tank 2 enters the electrodialysis device 3, and produces fresh water, concentrated water and polar water under the action of electrodialysis, wherein the fresh water is discharged into the fresh water intermediate tank 5, and the concentrated water and polar water are mixed and discharged into the concentrated water intermediate tank 4, and the pH is adjusted to 7-10 by adding liquid alkali. If the chloride ion content of the mixed concentrated water in the concentrated water intermediate tank 4 is lower than 1.0%, a certain amount of sodium chloride is added thereto;

[0081] S3: The mixed concentrated water with adjusted water quality in the concentrated water intermediate tank 4 enters the concentrated chamber 10 of the electrocatalytic oxidation tank 1 for electrocatalytic oxidation reaction, so that ammonia nitrogen is effectively removed, and then enters the first compartment 13 of the dilute chamber to be mixed with the fresh water from the fresh water intermediate tank 5 and undergo secondary oxidation reaction. The mixed wastewater in the first compartment 13 of the dilute chamber is discharged into the second compartment 29 of the dilute chamber for tertiary oxidation reaction, and finally discharged into the subsequent treatment system through the second compartment outlet 27

[0082] Below Figure 1 and Figure 2 The operation of the treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater is further described.

[0083] Example:

[0084] The low-salt wastewater used in the experiment came from a pesticide company in Jiangsu. The water quality was as follows: salt content 0.77% (mainly sodium chloride and ammonium chloride), COD value 2239 mg / L, ammonia nitrogen 816 mg / L, and pH value 9.49.

[0085] For this low-salinity wastewater, Figure 1 and Figure 2 The treatment system shown in the figure is used for efficient denitrification, and the steps are as follows:

[0086] S1: Low-salt wastewater enters the water distribution tank 2 and is adjusted to pH 6 by adding hydrochloric acid;

[0087] S2: The low-salt wastewater with pH adjusted in the water inlet distribution tank 2 enters the electrodialysis device 3, and produces fresh water, concentrated water and polar water under the action of electrodialysis, wherein the fresh water is discharged into the fresh water intermediate tank 5; the concentrated water and polar water are discharged into the concentrated water intermediate tank 4, and the pH is adjusted to 9 by adding liquid alkali;

[0088] S3: The mixed concentrated water with adjusted pH in the concentrated water intermediate tank 4 enters the concentrated water chamber 10 of the electrocatalytic oxidation tank 1 for electrocatalytic oxidation reaction. A titanium plate is used as the cathode and IrO2-RuO2 / Ti is used as the anode. Direct current is passed through the cathode plate and the anode plate. The current density is controlled to be 500A / m 2 , so that the ammonia nitrogen is effectively removed, and then enters the first compartment 13 of the dilute chamber, mixes with all the fresh water from the fresh water intermediate pool 5 and undergoes a secondary oxidation reaction; the mixed wastewater in the first compartment 13 of the dilute chamber is discharged into the second compartment 29 of the dilute chamber, undergoes a tertiary oxidation reaction, and is finally discharged into the subsequent treatment system through the second compartment outlet 27.

[0089] During the above treatment process, the changes in wastewater quality are shown in the following table:

[0090]

[0091]

[0092] Compared with low-salinity wastewater, the final effluent has a 74.6% lower ammonia nitrogen concentration, a 7.3% lower COD concentration, and a slightly lower salt content. During the treatment process, the power consumption of electrodialysis is 2kW / t wastewater, the power consumption of electrocatalytic oxidation is 20kW / t wastewater, and the total power consumption is 22kW / t wastewater.

[0093] Comparative Example 1:

[0094] This comparative example 1 uses conventional electrocatalytic oxidation technology to treat the low-salt wastewater (without salt supplementation) in the example. The treatment process is:

[0095] The low-salt wastewater is adjusted to pH 9 by adding hydrochloric acid, and then enters the concentration chamber 10 of the electrocatalytic oxidation tank 1 to undergo an electrocatalytic oxidation reaction under the same experimental conditions (water volume, time, electrode plates, current density, etc.) as in the embodiment.

[0096] During the above treatment process, the changes in wastewater quality are shown in the following table:

[0097] Wastewater name COD(mg / L) <![CDATA[NH3-N(mg / L)]]> Salt content Low salt wastewater 2239 816 0.77％ Final water discharge 1924 577 0.76％

[0098] Compared with low-salinity wastewater, the final effluent has ammonia nitrogen concentration reduced by 29.3%, COD concentration reduced by 14.1%, and the salt content remains basically unchanged. During the treatment process, the voltage required for electrocatalytic oxidation is significantly higher than that of the embodiment, and the total power consumption reaches 32kW / t wastewater.

[0099] Compared with Comparative Example 1, the treatment system and process adopted in the embodiment have a 45.3% higher removal rate of ammonia nitrogen, a higher denitrification selectivity, a 73.0% reduction in energy consumption per unit mass of ammonia nitrogen removal, and a significantly reduced denitrification cost. Therefore, the treatment system and process provided by the present invention have obvious advantages over conventional electrocatalytic oxidation technology (without salt supplementation).

[0100] Comparative Example 2:

[0101] This comparative example 2 uses conventional electrocatalytic oxidation technology to treat the low-salt wastewater in the example (adding 15g / L sodium chloride). The treatment process is:

[0102] The low-salt wastewater is adjusted to pH 9 by adding hydrochloric acid, and then 15 g / L sodium chloride is added, and then enters the concentration chamber 10 of the electrocatalytic oxidation cell 1 to perform an electrocatalytic oxidation reaction under the same experimental conditions (water volume, time, electrode plates and current density, etc.) as in the embodiment.

[0103] During the above treatment process, the changes in wastewater quality are shown in the following table:

[0104] Wastewater name COD(mg / L) <![CDATA[NH3-N(mg / L)]]> Salt content Low salt wastewater 2239 816 0.77％ Final water discharge 1753 427 2.30％

[0105] Compared with low-salinity wastewater, the final effluent has ammonia nitrogen concentration reduced by 47.7% and COD concentration reduced by 21.7%, but the salt content is significantly increased. During the treatment process, the voltage required for electrocatalytic oxidation is slightly higher than that of the embodiment, and the total power consumption is 22kW / t wastewater.

[0106] Compared with Comparative Example 2, the treatment system and process adopted in the embodiment have a 26.9% higher removal rate of ammonia nitrogen, a higher denitrification selectivity, a 36.0% reduction in energy consumption per unit mass of ammonia nitrogen removal, a significantly reduced treatment cost, and a lower final effluent salt content, which has less impact on subsequent biochemical systems. Therefore, the treatment system and process provided by the present invention have obvious advantages over conventional electrocatalytic oxidation technology (salt supplementation).

[0107] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0108] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0109] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater, characterized in that: include: An electrocatalytic oxidation tank (1), an inlet distribution tank (2), an electrodialysis device (3), a concentrated water intermediate tank (4) and a fresh water intermediate tank (5); the electrocatalytic oxidation tank (1) provides a reaction site for ammonia nitrogen removal, and the electrocatalytic oxidation tank (1) comprises a concentrated chamber (10), a first compartment of a fresh water chamber (13) and a second compartment of a fresh water chamber (29); the inlet distribution tank (2) receives low-salinity wastewater to be treated, and is connected to the water inlet of the electrodialysis device (3) through a pump and a pipeline; the concentrated water intermediate tank (4) receives concentrated water and polar water produced by the electrodialysis device (3), and is connected to the electrocatalytic oxidation tank (1) through a pump and a pipeline; the fresh water intermediate tank (5) receives fresh water produced by the electrodialysis device (3), and is connected to the electrocatalytic oxidation tank (1) through a pump and a pipeline; The first compartment (13) of the dilution chamber comprises an aeration system (7), the aeration system (7) is connected to a concentration chamber air outlet (17) via an air outlet pipe (14), and the concentration chamber air outlet (17) is arranged at the upper part of the concentration chamber (10); The second compartment (29) of the dilution chamber comprises a second aeration system (12), and the second aeration system (12) is connected to a second gas outlet (25) of the concentration chamber via a second gas outlet pipe (26), and the second gas outlet (25) of the concentration chamber is arranged at the upper part of the concentration chamber (10).

2. A treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater according to claim 1, characterized in that: The concentrated chamber (10) is located between the first cell (13) of the dilute chamber and the second cell (29) of the dilute chamber. An electrocatalytic plate group (9) is arranged in the concentrated chamber (10). The concentrated water intermediate tank (4) is connected to a concentrated chamber water inlet (16) of the concentrated chamber (10). The concentrated chamber water inlet (16) is arranged at the upper part of the concentrated chamber (10) and is higher than the top of the electrocatalytic plate group (9). The dilute water intermediate tank (5) is connected to a first cell water inlet (6) of the first cell (13) of the dilute chamber. The first cell water inlet (6) is arranged at the lower part of the first cell (13) of the dilute chamber.

3. A treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater according to claim 1, characterized in that: The concentration chamber (10) further comprises: The concentrated chamber water outlet (8) is arranged at the lower part of the concentrated chamber (10) and communicates with the concentrated chamber (10) and the first compartment (13) of the dilute chamber.

4. A treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater according to claim 1, characterized in that: The concentration chamber (10) further comprises: A pressure gauge (20), the pressure gauge (20) is arranged at the top of the concentration chamber (10) and is used to monitor the gas pressure in the concentration chamber (10); A liquid level meter (21), the liquid level meter (21) is arranged in the concentration chamber (10) and is used to monitor the wastewater liquid level in the concentration chamber (10); A mechanical stirring device (28) is arranged in the concentration chamber (10) and is used to stir and mix the wastewater in the concentration chamber (10).

5. A treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater according to claim 3, characterized in that: The first section of the Tanshi (13) also includes: A first water outlet (15), which is disposed at the upper portion of the first water outlet (13) of the dilute chamber and connected to the second water outlet (29) of the dilute chamber via a pipeline; A first air inlet (18), which is arranged at the top of the first air inlet (13) of the dilute chamber, and connects the first air inlet (13) of the dilute chamber with the outside atmosphere; The first compartment exhaust port (19) is arranged at the top of the first compartment (13) of the dilute chamber and is connected to the second compartment (29) of the dilute chamber through a pipeline.

6. A treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater according to claim 5, characterized in that: The second section of the light room (29) also includes: A second compartment water inlet (11), the second compartment water inlet (11) is arranged at the lower part of the second compartment (29) of the desalination chamber, and the second compartment water inlet (11) is connected to the first compartment water outlet (15) through a pipeline; A second water outlet (27), which is disposed at the upper portion of the second water outlet (29) of the desalination chamber; A second compartment air inlet (22), the second compartment air inlet (22) is arranged at the top of the second compartment (29) of the dilute chamber, and the second compartment air inlet (22) is connected to the first compartment air outlet (19) through a pipeline; The second compartment exhaust port (24) is arranged at the top of the second compartment (29) of the dilute chamber, and is connected to the induced draft fan (23) through a pipeline to lead the waste gas generated by the entire electrocatalytic oxidation tank (1) to the waste gas treatment system.

7. A treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater according to claim 2, characterized in that: The anode plate on the electrocatalytic plate group (9) is set as a titanium plate coated with one or more materials selected from ruthenium, iridium, tantalum and platinum, and the anode plate is connected to the positive electrode of a direct current power source; the cathode plate on the electrocatalytic plate group (9) is set as any one of a titanium plate, a copper plate, stainless steel and graphite, and the cathode plate is connected to the negative electrode of the direct current power source; the current density on the plate is controlled to be 100-800A / m 2 .

8. A treatment system for efficiently removing ammonia nitrogen from low-salinity wastewater according to claim 1, characterized in that: The total salt content of the low-salt wastewater to be treated is less than 1.5%, the chloride ion content is less than 1.0%, and the ammonia nitrogen content is 100-4000 mg / L.

9. A process for efficiently removing ammonia nitrogen from low-salinity wastewater using the treatment system as described in any one of claims 1 to 8, the steps of which are: S1: The low-salinity wastewater to be treated enters the water distribution tank (2) and is adjusted to pH 4-6 by adding hydrochloric acid or liquid alkali; S2: The low-salt wastewater with adjusted pH in the water inlet distribution tank (2) enters the electrodialysis device (3), and produces fresh water, concentrated water and polar water under the action of electrodialysis, wherein the fresh water is discharged into the fresh water intermediate tank (5), and the concentrated water and polar water are mixed and discharged into the concentrated water intermediate tank (4), and the pH is adjusted to 7-10 by adding liquid alkali. If the chloride ion content of the mixed concentrated water in the concentrated water intermediate tank (4) is lower than 1.0%, a certain amount of sodium chloride is added thereto; S3: The mixed concentrated water with adjusted water quality in the concentrated water intermediate tank (4) enters the concentrated chamber (10) of the electrocatalytic oxidation tank (1) for electrocatalytic oxidation reaction, so that ammonia nitrogen is effectively removed, and then enters the first compartment (13) of the dilute chamber to be mixed with the fresh water from the fresh water intermediate tank (5) and undergo secondary oxidation reaction. The mixed wastewater in the first compartment (13) of the dilute chamber is discharged into the second compartment (29) of the dilute chamber for tertiary oxidation reaction, and finally discharged into the subsequent treatment system through the second compartment outlet (27).

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