An ammonia nitrogen recovery device and a method for recovering ammonia nitrogen in waste liquid

Abstract

This invention belongs to the field of wastewater treatment, and particularly relates to an ammonia nitrogen recovery device and a method for recovering ammonia nitrogen from wastewater. The ammonia nitrogen recovery device includes an electrodialysis unit and an ammonia nitrogen recovery unit. The electrodialysis unit includes a reaction tank, an anode assembly, a cathode assembly, and a cation exchanger. The cation exchanger includes an electroactive microbial culture unit for cultivating electroactive microorganisms. The electroactive microorganisms decompose organic matter in the ammonia nitrogen-containing wastewater to generate electrons. These electrons are transferred to the cathode assembly through an external circuit, increasing the pH of the catholyte in the cathode chamber of the cation exchanger. Ammonia nitrogen is transferred to the cathode assembly through the cation exchange membrane, where ammonium ions are converted into free ammonia. A catholyte circulation loop is provided between the electrodialysis unit and the ammonia nitrogen recovery unit. Free ammonia travels with the catholyte through the catholyte circulation loop to the ammonia nitrogen recovery unit, where it is absorbed by the absorbent and recovered as ammonia nitrogen. The entire process does not require the addition of alkaline reagents, thus reducing costs.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, specifically to an ammonia nitrogen recovery device and a method for recovering ammonia nitrogen from waste liquid. Background Technology

[0002] In recent years, with the development of industrial technology, a large amount of industrial wastewater has been discharged into the water environment. Among the industrial wastewater, sludge digestion liquid, coking wastewater and leachate from old landfills are characterized by high ammonia nitrogen levels. How to recover ammonia nitrogen from wastewater has attracted widespread attention.

[0003] Traditional ammonia nitrogen recovery methods employ stripping, which involves introducing alkaline substances into wastewater to convert ammonium ions into free ammonia. The wastewater is then passed through a stripping tower for aeration and stripping, and finally, the free ammonia is absorbed by the absorbent. However, the cost of alkaline agents is relatively high, and the addition of these agents to convert ammonium ions into free ammonia results in high costs, hindering the company's economic efficiency. Therefore, it is necessary to further develop methods for recovering ammonia nitrogen from wastewater to improve recovery efficiency and reduce operating costs. Summary of the Invention

[0004] To overcome the high cost of traditional ammonia nitrogen recovery methods, this invention provides an ammonia nitrogen recovery device and a method for recovering ammonia nitrogen from wastewater. Electroactive microorganisms cultured in an electroactive microbial culture medium decompose organic matter in wastewater (wastewater) to generate electrons. These electrons are transferred to a cathode assembly to increase the pH of the cathode solution, eliminating the need for additional alkaline agents and reducing costs.

[0005] To solve the above-mentioned technical problems, another technical solution adopted in this embodiment of the invention is: providing an ammonia nitrogen recovery device, including: an electrodialysis mechanism, including a reaction tank, an anode assembly, a cathode assembly, and a cation exchanger; the reaction tank is provided with a reaction chamber for containing waste liquid containing ammonia nitrogen; the cation exchanger is disposed in the reaction chamber and is provided with a cathode chamber, a first cathode liquid inlet connector, and a first cathode liquid outlet connector, both of which are connected to the cathode chamber; the cathode assembly is disposed in the cathode chamber; the anode assembly includes an anode element and an electroactive microbial culture element; the anode element surrounds the cation exchanger; the electroactive microbial culture element is disposed on the anode element and is used to cultivate electroactive microorganisms, which decompose organic matter in the waste liquid containing ammonia nitrogen and generate electrons; and an ammonia nitrogen recovery mechanism, including an ammonia nitrogen recovery mechanism body, a second cathode liquid inlet connector, a second cathode liquid outlet connector, an absorbent liquid inlet connector, and an absorbent liquid outlet connector, the second cathode liquid inlet connector, the second cathode liquid outlet connector, the second cathode liquid outlet connector, the absorbent liquid inlet connector, and the absorbent liquid outlet connector, the second cathode liquid inlet connector, the second cathode liquid outlet connector, the second cathode liquid outlet connector, the second cathode liquid outlet connector, the absorbent liquid outlet connector, the second cathode ... The cathode liquid inlet, the second cathode liquid outlet, the absorbent liquid inlet, and the absorbent liquid outlet are all connected to the ammonia nitrogen recovery mechanism body. The second cathode liquid inlet is connected to the first cathode liquid outlet, and the second cathode liquid outlet is connected to the first cathode liquid inlet, so that a cathode liquid circulation loop is formed between the cathode cavity and the ammonia nitrogen recovery mechanism. The cathode liquid circulation loop is used to supply cathode liquid flow. The absorbent liquid inlet is used to supply absorbent liquid, and the absorbent liquid outlet is used to supply absorbent liquid output. When the cathode assembly and the anode assembly are energized, ammonium ions in the ammonia nitrogen-containing waste liquid enter the cathode cavity through the cation exchange element and are placed in the cathode liquid. The electroactive microorganisms decompose the organic matter in the ammonia nitrogen-containing waste liquid to generate electrons. The electrons are transferred to the cathode assembly through the energizing circuit to increase the pH of the cathode liquid in the cathode cavity and convert ammonium ions into free ammonia. The ammonia nitrogen recovery mechanism is used to transfer the free ammonia to the absorbent liquid entering through the absorbent liquid inlet and absorb it by the cathode liquid, and output it from the absorbent liquid outlet.

[0006] Optionally, the cation exchanger includes an upper cap, an upper tube, a cation exchange membrane tube, and a lower cap; the upper tube has an upper cavity, the upper cap is placed over one end of the upper tube, the first cathode liquid inlet and the first cathode liquid outlet are located on the upper cap, and the first cathode liquid inlet and the first cathode liquid outlet are connected to the upper cavity; the cation exchange membrane tube has a lower cavity, the other end of the upper tube is connected to one end of the cation exchange membrane tube, the lower cap is placed over the other end of the cation exchange membrane tube to close the other end of the cation exchange membrane tube, the upper cavity and the lower cavity are connected to form a cathode cavity, and the cation exchange membrane tube allows ammonium ions to pass through.

[0007] Optionally, the cation exchanger further includes an external support tube, which is sleeved outside the cation exchange membrane tube. One end of the external support tube is fixed to the upper tube, and the other end of the external support tube is fixed to the reaction chamber. The external support tube is provided with an opening that allows the ammonia-nitrogen-containing waste liquid to pass through.

[0008] Optionally, the cation exchanger further includes an inlet pipe located in the cathode cavity, one end of which is connected to a first cathode liquid inlet connector, and the other end of which extends toward the lower cap; the cathode assembly is tubular, one end of which is connected to the first cathode liquid outlet connector, and the other end of which extends toward the lower cap.

[0009] Optionally, the cathode assembly has openings in its tube wall that allow gas and liquid to pass through.

[0010] Optionally, the ammonia nitrogen recovery device further includes a transfer tank, which is provided with a transfer chamber, a third cathode liquid inlet connector, a third cathode liquid outlet connector, a fourth cathode liquid inlet connector, and a fourth cathode liquid outlet connector. The third cathode liquid inlet connector, the third cathode liquid outlet connector, the fourth cathode liquid inlet connector, and the fourth cathode liquid outlet connector are all connected to the transfer chamber. The third cathode liquid inlet connector is connected to the first cathode liquid outlet connector, the third cathode liquid outlet connector is connected to the first cathode liquid inlet connector, the fourth cathode liquid inlet connector is connected to the second cathode liquid outlet connector, and the fourth cathode liquid outlet connector is connected to the second cathode liquid inlet connector.

[0011] Optionally, the ammonia nitrogen recovery device further includes a first valve body, which is disposed on the connection between the second cathode liquid inlet connector and the ammonia nitrogen recovery mechanism body.

[0012] Optionally, the ammonia nitrogen recovery device further includes a second valve body, which is disposed on the connection between the absorbent inlet connector and the ammonia nitrogen recovery mechanism body.

[0013] Optionally, the ammonia nitrogen recovery device further includes a pressure gauge, which is installed on the connection between the absorbent inlet and the ammonia nitrogen recovery mechanism body.

[0014] To solve the above-mentioned technical problems, another technical solution adopted in this embodiment of the invention is: providing a method for recovering ammonia nitrogen from waste liquid, applied to the above-mentioned ammonia nitrogen recovery device, the method comprising: inoculating the reaction chamber with a strain containing the electroactive microorganisms; continuously injecting waste liquid containing ammonia nitrogen into the reaction chamber, and energizing the cathode assembly and the anode assembly; gradually increasing the tank voltage when the potential of the anode assembly is within a preset potential range; controlling the flow of cathode liquid in the cathode liquid circulation loop when the potential of the anode assembly is within the preset potential range and the current between the cathode assembly and the anode assembly is stable; and controlling the absorbent liquid to be input from the absorbent liquid inlet and output from the absorbent liquid outlet.

[0015] This invention provides an ammonia nitrogen recovery device. In an electrodialysis unit, the anode assembly includes an electroactive microbial culture element for cultivating electroactive microorganisms. When the cathode and anode assemblies are energized, the electroactive microorganisms decompose organic matter in the ammonia-nitrogen-containing waste liquid and generate electrons. These electrons are transferred to the anode assembly through the electron transport process of the microorganisms, and then led to the cathode assembly via the energizing circuit. At this time, in order to maintain charge balance, positively charged ions such as ammonium ions (NH4+) are released. + The catholyte, carrying a positive charge, passes through the cation exchanger and enters the cathode chamber. The catholyte, upon gaining electrons, undergoes oxygen reduction or hydrogen ion reduction to produce OH-. - This causes the pH of the catholy solution to rise, leading to an increase in the amount of NH4+ transferred to the catholy solution. + The ammonia is converted into free ammonia. The free ammonia flows from the cathode chamber through the cathode liquid circulation loop to the ammonia nitrogen recovery mechanism. This mechanism transfers the free ammonia (NH3) from the cathode liquid to the absorbent liquid entering through the absorbent inlet. The absorbent liquid absorbs the free ammonia, and then exits through the absorbent liquid outlet, thus achieving ammonia nitrogen recovery. The entire process requires no additional alkaline reagents, reducing costs. Attached Figure Description

[0016] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0017] Figure 1 This is a schematic diagram of the overall structure of the electrodialysis mechanism in an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of the overall structure of the combined module in an embodiment of the present invention;

[0019] Figure 3 This is a left view of the combined module in an embodiment of the present invention;

[0020] Figure 4 This is a top view of the combined module in an embodiment of the present invention;

[0021] Figure 5 This is a schematic diagram of the overall structure of the cation exchanger in an embodiment of the present invention;

[0022] Figure 6 yes Figure 5 Enlarged view of point A in the middle;

[0023] Figure 7 This is a left view of the cation exchanger in an embodiment of the present invention;

[0024] Figure 8 This is a schematic diagram of the overall structure of the ammonia nitrogen recovery mechanism in an embodiment of the present invention;

[0025] Figure 9 This is a schematic diagram of the overall structure of the transfer barrel in an embodiment of the present invention.

[0026] Explanation of reference numerals in the attached figures:

[0027] 100. Electrodialysis facility;

[0028] 11. Reaction chamber; 110. Reaction cavity; 12. Anode assembly; 13. Cathode assembly; 14. Cation exchange unit; 140. Cathode cavity; 141. First catholyte inlet connector; 142. First catholyte outlet connector; 143. Upper cap; 144. Upper tube; 1440. Upper cavity; 145. Anode membrane tube; 1450. Lower cavity; 146. Lower cap; 147. Inlet tube; 148. External support tube; 149. Internal support tube;

[0029] 200. Ammonia nitrogen recovery facility;

[0030] 20. Ammonia nitrogen recovery mechanism body; 21. Second cathode liquid inlet connector; 22. Second cathode liquid outlet connector; 23. Absorbent liquid inlet connector; 24. Absorbent liquid outlet connector; 25. First valve body; 26. Second valve body; 27. First pump body; 28. Second pump body; 29. ​​Pressure gauge;

[0031] 300, transfer barrels;

[0032] 300. Transfer chamber; 31. Third catholyte inlet connector; 32. Third catholyte outlet connector; 33. Fourth catholyte inlet connector; 34. Fourth catholyte outlet connector; 35. Stirrer; 36. Gas outlet connector.

[0033] 400. Combination Module. Detailed Implementation

[0034] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0035] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "circumferential," and "radial," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0038] Please see Figure 1 and Figure 8 The ammonia nitrogen recovery device includes an electrodialysis unit 100 and an ammonia nitrogen recovery unit 200. The electrodialysis unit 100 is connected to the ammonia nitrogen recovery unit 200. The electrodialysis unit 100 is used to convert ammonium ions (NH4+) in the waste liquid containing ammonia nitrogen into free ammonia (NH3). The free ammonia is transferred to the ammonia nitrogen recovery unit 200 and recovered by the ammonia nitrogen recovery unit 200.

[0039] For the aforementioned electrodialysis unit 100, please refer to Figures 1 to 4The electrodialysis unit 100 includes a reaction chamber 11, an anode assembly 12, a cathode assembly 13, and a cation exchanger 14. The reaction chamber 11 is provided with a reaction chamber 110, which is used to contain waste liquid containing ammonia nitrogen. The anode assembly 12 and the cation exchanger 14 are disposed in the reaction chamber 110, and the anode assembly 12 can be arranged around the cation exchanger 14 to reduce the space occupied. The cation exchanger 14 is provided with a cathode chamber 140, a first cathode liquid inlet connector 141, and a first cathode liquid outlet connector 142. The cathode chamber 140 is used to contain cathode liquid. The first cathode liquid inlet connector 141 and the first cathode liquid outlet connector 142 are both connected to the cathode chamber 140 so that cathode liquid can be input into or output from the cathode chamber 140. The first cathode liquid inlet connector 141 and the first cathode liquid outlet connector 142 are used to connect with the ammonia nitrogen recovery unit 200 and form a cathode liquid circulation loop between the cathode chamber 140 and the ammonia nitrogen recovery unit 200. The cathode assembly 13 is disposed in the cathode chamber 140. When the cathode assembly 13 and the anode assembly 12 are energized, they can be used for electrodialysis treatment of waste liquid containing ammonia nitrogen.

[0040] It should be noted that the above-mentioned reaction tank 11 is only a general term for the reaction site. The reaction tank 11 does not need to have a specific shape. The reaction tank 11 can refer to any reaction site containing waste liquid containing ammonia nitrogen. In the embodiments of the present invention, the anode assembly 12, the cathode assembly 13 and the cation exchanger 14 can be placed in different reaction tanks 11 as a combined module 400, forming an electrodialysis mechanism 100 with the reaction tank 11.

[0041] The anode assembly 12 described above includes an anode element (not shown) and an electroactive microbial culture element (not shown). The anode element is arranged around the cation exchange element 14 to save space. The electroactive microbial culture element is fixedly disposed on the anode element and is used to cultivate electroactive microorganisms. The electroactive microbial culture element provides an attachment surface for the electroactive microorganisms to form a stable biofilm. The electroactive microorganisms decompose organic matter in the ammonia-nitrogen-containing waste liquid and generate electrons. Optionally, the anode element can be a conductive material with multiple openings, which allow the ammonia-nitrogen waste liquid to pass through and contact the electroactive microorganisms on the electroactive microbial culture element, so that the electroactive microorganisms can obtain organic nutrients from the waste liquid. Optionally, the electroactive microbial culture element can be a carbon felt, etc., which can provide a good attachment surface for the growth of electroactive microorganisms.

[0042] For the cation exchange element 14 mentioned above, please refer to Figures 5 to 7The cation exchange unit 14 includes an upper cap 143, an upper tube 144, a cation exchange membrane tube 145, a lower cap 146, an inlet tube 147, an outer support tube 148, and an inner support tube 149. The upper tube 144 has an upper cavity 1440, and the upper cap 143 is placed over one end of the upper tube 144 to seal that end. The other end of the upper tube 144 is connected to one end of the cation exchange membrane tube 145. The cation exchange membrane tube 145 has a lower cavity 1450, and the lower cap 146 is placed over the other end of the cation exchange membrane tube 145 to seal that end. The upper cavity 1440 and the lower cavity 1450 are connected to form a cathode cavity 140, while the cation exchange membrane tube 145 allows cations such as ammonium ions to pass through. A first cathode liquid inlet connector 141 is disposed on the upper cap 143 and is connected to the upper cavity 1440. One end of the inlet pipe 147 is connected to the first cathode liquid inlet connector 141, and the other end of the inlet pipe 147 extends downward to the cap 146, so that cathode liquid can enter the cathode cavity 140 through the first cathode liquid inlet connector 141 and the inlet pipe 147. A first cathode liquid outlet connector 142 is disposed on the upper cap 143 and is connected to the upper cavity 1440. A cathode assembly 13 is disposed inside the cathode cavity 140. The cathode assembly 13 is tubular, and one end of the cathode assembly 13 is connected to the first cathode liquid outlet connector 142. The other end of the cathode assembly 13 extends downward to the cap 146, so that cathode liquid can be output from the cathode cavity 140 through the first cathode liquid outlet connector 142 and the cathode assembly 13. Optionally, the tube wall of the cathode assembly 13 may be provided with one or more openings, which allow gas and liquid to pass through, so that gas and liquid can pass through the tube wall of the cathode assembly 13 and be directly output from the first cathode liquid outlet joint 142 in an overflow manner. The gas generated in the cathode cavity 140 due to the reaction can directly pass through the cathode assembly 13 and be directly output from the first cathode liquid outlet joint 142, thus avoiding gas accumulation in the cathode cavity 140. An outer support tube 148 is sleeved around the cation exchange membrane tube 145 and fixed to it to support the cation exchange membrane tube 145 and prevent it from being physically damaged by substances in the waste liquid during use, thus protecting the cation exchange membrane tube 145. The outer support tube 148 can be fixed to the cation exchange membrane tube 145 in different ways. For example, one end of the outer support tube 148 can be fixed to the upper tube 144 and the other end can be fixed to the lower tube cap 146; or, one end of the outer support tube 148 can be fixed to the upper tube 144 and the other end can be fixed to another position in the reaction chamber 110. The outer support tube 148 is provided with an opening that allows waste liquid containing ammonia nitrogen to pass through, so that the waste liquid containing ammonia nitrogen can contact the cation exchange membrane tube 145 for cation exchange. An inner support tube 149 is sleeved inside the cation exchange membrane tube 145 to protect the inner side of the cation exchange membrane tube 145. One end of the inner support tube 149 is fixed to the upper tube 144, and the other end is fixed to the lower tube cap 146 to support the upper tube 144.To ensure that the outer support tube 148 and the inner support tube 149 provide good support and protection, both the outer support tube 148 and the inner support tube 149 are made of rigid materials.

[0043] In some embodiments, the cation exchanger 14 further includes tabs (not shown) disposed on the upper cap 143 and at least partially exposed outside the upper cap 143. The tabs are welded to the cathode assembly 13, facilitating connection of the cathode assembly 13 to the anode assembly 12 via the tabs. In other embodiments, the cathode assembly 13 may be connected in other ways, for example, at least a portion of the cathode assembly 13 may pass through the upper cap 143 and be exposed outside the upper cap 143; this is not limited by the present invention.

[0044] In some embodiments, the electrodialysis unit 100 may include a plurality of cation exchangers 14, which are connected sequentially. The first catholyte outlet 142 of the preceding cation exchanger 14 is connected to the first catholyte inlet 141 of the adjacent following cation exchanger 14, thereby forming a catholyte flow loop among the plurality of cation exchangers 14. The first catholyte inlet 141 of the first cation exchanger 14 is connected to the second catholyte outlet 22, and the first catholyte outlet 142 of the last cation exchanger 14 is connected to the second catholyte inlet 21, thereby forming a catholyte circulation loop. The anode assembly 12 is arranged around each cation exchanger 14 to reduce the space occupied. Optionally, the plurality of cation exchangers 14 may be connected sequentially in an S-shape to make the whole unit more compact. With the increase of cation exchangers 14, the treatment efficiency of wastewater containing ammonia nitrogen can be improved.

[0045] The working principle of the electrodialysis unit 100 is as follows: The anode assembly 12 includes an electroactive microbial culture element, which is used to cultivate electroactive microorganisms. When the cathode assembly 13 and the anode assembly 12 are connected to the power supply, the electroactive microorganisms decompose the organic matter in the waste liquid containing ammonia nitrogen and generate electrons. The electrons are transferred to the anode assembly 12 through the electron transfer process of the microorganisms, and then led to the cathode assembly 13 through the power connection circuit. At this time, in order to maintain charge balance, positively charged ions such as ammonium ions (NH4+) will carry positive charges and enter the catholyte in the cathode chamber 140 through the anolyte tube 145. The catholyte undergoes oxygen reduction or hydrogen ion reduction processes due to gaining electrons, generating OH-, thereby increasing the pH of the catholyte and converting the NH4+ transferred to the catholyte into free ammonia. This process does not require the addition of alkaline reagents. The free ammonia can flow from the cathode chamber 140 to the ammonia nitrogen recovery unit 200 through the catholyte circulation loop, and is thus recovered by the ammonia nitrogen recovery unit 200.

[0046] For the aforementioned ammonia nitrogen recovery unit 200, please refer to Figure 8The ammonia nitrogen recovery mechanism 200 includes an ammonia nitrogen recovery mechanism body 20, a second cathode liquid inlet connector 21, a second cathode liquid outlet connector 22, an absorbent liquid inlet connector 23, an absorbent liquid outlet connector 24, a first valve body 25, a second valve body 26, a first pump body 27, a second pump body 28, and a pressure gauge 29. The ammonia nitrogen recovery mechanism body 20 is provided with a hydrophobic and breathable membrane (not shown), a first inner cavity (not shown), and a second inner cavity (not shown). The hydrophobic and breathable membrane separates the first and second inner cavities. The first inner cavity is used to contain the cathode liquid, and the second inner cavity is used to contain the absorbent liquid. Free ammonia in the cathode liquid can pass through the hydrophobic and breathable membrane to reach the absorbent liquid. The second cathode liquid inlet connector 21 and the second cathode liquid outlet connector 22 are connected to the ammonia nitrogen recovery mechanism body 20 and communicate with the first inner cavity, so that the cathode liquid can be input into or output from the first inner cavity. The second cathode liquid inlet connector 21 is connected to the first cathode liquid outlet connector 142, and the second cathode liquid outlet connector 22 is connected to the first cathode liquid inlet connector 141, so that a cathode liquid circulation loop is formed between the cathode chamber 140 and the ammonia nitrogen recovery mechanism 200. The cathode liquid circulation loop is used to supply cathode liquid flow. The absorbent liquid inlet connector 23 and the absorbent liquid outlet connector 24 are both connected to the ammonia nitrogen recovery mechanism body 20 and communicate with the second inner cavity. The absorbent liquid inlet connector 23 is used to supply absorbent liquid, and the absorbent liquid outlet connector 24 is used to supply absorbent liquid output. The first valve body 25 is disposed on the connection between the second cathode liquid inlet connector 21 and the ammonia nitrogen recovery mechanism body 20, and the first valve body 25 is used to control the flow rate of the cathode liquid. The second valve body 26 is disposed on the connection between the absorbent liquid inlet connector 23 and the ammonia nitrogen recovery mechanism body 20, and the second valve body 26 is used to control the flow rate of the absorbent liquid. A first pump body 27 is installed on the connection between the second cathode liquid inlet connector 21 and the ammonia nitrogen recovery mechanism body 20, and is used to pump cathode liquid. A second pump body 28 is installed on the connection between the absorbent liquid inlet connector 23 and the ammonia nitrogen recovery mechanism body 20, and is used to pump absorbent liquid. A pressure gauge 29 is installed on the connection between the absorbent liquid inlet connector 23 and the ammonia nitrogen recovery mechanism body 20, and is used to measure the pressure inside the pipeline.

[0047] In some embodiments, the absorbent is an acidic absorbent, such as a hydrochloric acid solution or a sulfuric acid solution or a mixture thereof, to convert free ammonia into ammonium ions, thereby recovering ammonia nitrogen from the catholyte.

[0048] The working principle of the ammonia nitrogen recovery mechanism 200 is as follows: free ammonia is carried by the catholyte through the catholyte circulation loop to the first inner cavity, and the absorbent flows from the absorbent inlet connector 23 to the second inner cavity. The free ammonia in the first inner cavity passes through the hydrophobic and breathable membrane to the second inner cavity and is absorbed by the absorbent. The absorbent is output from the absorbent outlet connector 24, thereby completing the recovery of ammonia nitrogen.

[0049] In some embodiments, please refer to Figure 9 The ammonia nitrogen recovery device also includes a transfer tank 300, which is equipped with a transfer chamber 30, a third cathode liquid inlet connector 31, a third cathode liquid outlet connector 32, a fourth cathode liquid inlet connector 33, a fourth cathode liquid outlet connector 34, a stirrer 35, and a gas outlet connector 36. The third cathode liquid inlet connector 31 and the third cathode liquid outlet connector 32 are both connected to the transfer chamber 30, and the third cathode liquid inlet connector 31 is connected to the first cathode liquid outlet connector 142, and the third cathode liquid outlet connector 32 is connected to the first cathode liquid inlet connector 141, so that a first cathode liquid circulation loop is formed between the cathode chamber 140 and the transfer chamber 30. The first cathode liquid circulation loop is used to supply cathode liquid flow. Both the fourth cathode liquid inlet connector 33 and the fourth cathode liquid outlet connector 34 are connected to the transfer chamber 30, and the fourth cathode liquid inlet connector 33 is connected to the second cathode liquid outlet connector 22, so that a second cathode liquid circulation loop is formed between the transfer chamber 30 and the first inner chamber. The second cathode liquid circulation loop is used to supply cathode liquid flow. Thus, the cathode liquid can flow into the transfer chamber 30 through the first cathode liquid circulation loop and the second cathode liquid circulation loop to complete the transfer. The stirrer 35 is connected to the transfer tank 300, and the stirring end of the stirrer 35 is located in the transfer chamber 30. The stirrer 35 is used to stir the liquid in the transfer chamber 30 to make the liquid mix evenly. The gas generated by the reaction in the cathode chamber 140 can be input into the transfer chamber 30 through the first cathode liquid circulation loop. In order to balance the gas pressure, the transfer tank 300 is provided with a gas outlet connector 36, which is connected to the transfer chamber 30 and is used to collect the gas in the transfer chamber 30.

[0050] In this embodiment of the invention, the ammonia nitrogen recovery device includes an electrodialysis unit 100 and an ammonia nitrogen recovery unit 200. The electrodialysis unit 100 includes an anode assembly 12, which includes an electroactive microbial culture element. The electroactive microbial culture element is used to cultivate electroactive microorganisms. When the cathode assembly 13 and the anode assembly 12 are connected to the power supply, the electroactive microorganisms decompose the organic matter in the waste liquid containing ammonia nitrogen and generate electrons. The electrons are transferred to the anode assembly 12 through the electron transfer process of the microorganisms, and then led to the cathode assembly 13 through the power connection circuit. At this time, in order to maintain charge balance, positively charged ions such as ammonium ions (NH4+) will carry positive charges and enter the cathode liquid in the cathode cavity 140 through the anolyte tube 145. The cathode liquid generates OH- due to the oxygen reduction or hydrogen ion reduction process after gaining electrons, thereby increasing the pH of the cathode liquid and converting the NH4+ transferred to the cathode liquid into free ammonia. The ammonia nitrogen recovery mechanism 200 includes an ammonia nitrogen recovery mechanism body 20. The body 20 contains a first inner cavity, a second inner cavity, and a hydrophobic and breathable membrane. The membrane separates the first and second inner cavities. The first inner cavity contains catholyte, and the second inner cavity contains absorbent. Free ammonia in the catholyte can pass through the hydrophobic and breathable membrane to reach the absorbent. Free ammonia travels with the catholyte through the catholyte circulation loop to the first inner cavity. The absorbent flows from the absorbent inlet 23 to the second inner cavity. Free ammonia in the first inner cavity passes through the hydrophobic and breathable membrane to reach the second inner cavity and is absorbed by the absorbent. The absorbent is then output from the absorbent outlet 24, thus completing the recovery of ammonia nitrogen. The entire process requires no external alkaline reagent, reducing costs.

[0051] This invention also provides a method for recovering ammonia nitrogen from waste liquid, which is applied to the aforementioned ammonia nitrogen recovery device. The method includes:

[0052] Step S1: Inoculate the reaction chamber 110 with a strain containing electroactive microorganisms;

[0053] Step S2: Continuously inject waste liquid containing ammonia nitrogen into reaction chamber 110, and connect cathode assembly 13 and anode assembly 12 to power;

[0054] Step S3: When the potential of the anode assembly 12 is within the preset potential range, gradually increase the cell voltage;

[0055] Step S4: When the potential of the anode assembly 12 is within the preset potential range and the current between the cathode assembly 13 and the anode assembly 12 is stable, control the flow of the cathode liquid in the cathode liquid circulation loop, and control the absorption liquid to be input from the absorption liquid inlet connector 23 and output from the absorption liquid outlet connector 24.

[0056] In some embodiments, step S1 specifically involves inoculating the reaction chamber 110 with electroactive microorganisms by introducing sludge containing electroactive microorganisms into the reaction chamber 110 to provide electroactive microorganisms into the reaction chamber 110.

[0057] In some embodiments, step S2 specifically involves: continuously injecting ammonia-nitrogen-containing waste liquid into the reaction chamber 110 to provide organic nutrients required for the growth of electroactive microorganisms. The cathode assembly 13 and anode assembly 12 are energized to inhibit the growth of other bacterial species and screen for electroactive microorganisms. Optionally, the tank voltage can be controlled at 0.3V-1.0V to provide a favorable environment for the growth of electroactive microorganisms. Here, the tank voltage refers to the DC voltage applied between the anode assembly 12 and the cathode assembly 13.

[0058] In some embodiments, in step S3, the preset potential range is -0.4V to 0V. When the potential of the anode component 12 is within the preset range, it indicates that the electroactive microorganisms are growing well on the electroactive microorganism culture medium. When the potential of the anode component 12 is within the preset potential range, gradually increasing the tank voltage can increase the system current, thereby increasing the rate at which ammonium ions are converted into free ammonia.

[0059] After steps S1-S3, electroactive microorganisms grow into a film on the electroactive microorganisms, and the cultivation of electroactive microorganisms is basically completed, allowing for further treatment of the waste liquid containing ammonia nitrogen. When the potential of the anode component 12 is within the preset potential range and the current between the cathode component 13 and the anode component 12 is stable, the cathodic liquid in the cathodic liquid circulation loop is controlled to flow, and the absorbent is controlled to enter through the absorbent inlet connector 23 and exit through the absorbent outlet connector 24. This recovers ammonia nitrogen from the waste liquid. The relevant recovery principle can be found in the aforementioned content and will not be repeated here.

[0060] In short, the methods for recovering ammonia nitrogen from waste liquid mainly include two stages: the acclimatization stage and the production stage, as follows:

[0061] 1. Domestication stage

[0062] In the ammonia nitrogen recovery device, electrons are generated by electrogenic bacteria on electroactive microbial culture elements through the decomposition of organic matter. For example, inoculated sludge is added to the reaction chamber, maintaining a sludge concentration of 2-4 g / L, and then the wastewater to be treated is continuously introduced for biofilm acclimation culture. Optionally, the hydraulic retention time (HRT) is controlled between 10-40 h, maintaining the COD in the reaction chamber above 800 mg / L. Simultaneously, a voltage of 0.5 V is applied to the anode and cathode components to provide a favorable environment for electrogenic bacteria. The conductivity of the catholyte is similar to that of the wastewater to be treated, generally greater than 4 mS / cm. The catholyte circulation rate is between 50 L / h and 600 L / h, preferably 200 L / h-400 L / h. The catholyte circulation rate of the ammonia nitrogen recovery mechanism is 200-400 L / h, preferably 250 L / h. The absorbent is prepared using hydrochloric acid or sulfuric acid, preferably sulfuric acid, with a mass fraction of 2%-20%, preferably 8%-12%.

[0063] During the acclimatization and cultivation stage, to improve the survival environment for electrogenic bacteria, a cell voltage of 0.3V-1.0V, preferably 0.5V, needs to be provided between the anode and cathode components. Anode potential is an important indicator for evaluating the quality of microbial biofilm formation on the anode. Preferably, the anode component potential is controlled between -0.4V and -0V. Under this standard, the cell voltage is gradually increased to 2V-12V, thereby increasing the system current and thus improving the ammonia nitrogen recovery rate.

[0064] 2. Production Stage

[0065] The potential of the anode component is between -0.4V and 0V, the system current fluctuates little, and continuous production can be carried out. Based on the net removal of ammonia nitrogen in the wastewater to be treated, the actual required current is calculated, and the cell pressure is further adjusted.

[0066] To help readers better understand this invention, comparative experiments are conducted below.

[0067] Experiment 1: Using landfill leachate as wastewater to be treated

[0068] First, inoculum sludge was added to the reaction chamber to maintain the sludge concentration in the reaction zone at 2-4 g / L. Then, landfill leachate, which was used as the wastewater to be treated, was continuously fed in for biofilm acclimation and cultivation. The hydraulic retention time (HRT) was controlled at 25 h, and a cell voltage of 0.5 V was applied to the anode and cathode components. The potential of the anode component was controlled between -0.4 V and 0 V. Under this standard, the cell voltage was gradually increased to 5 V. Once the system current stabilized, the bio-electrodialysis system was considered successfully acclimated. In the actual recovery phase, the HRT was controlled at 10 h, 15 h, and 20 h, respectively. The catholyte circulation rate in the cathode chamber was 400 L / h, and the catholyte circulation rate in the ammonia nitrogen recovery mechanism was 200 L / h. Under these conditions, the water quality indicators and ammonia nitrogen recovery in the leachate are shown in Table 1 below.

[0069]

[0070] Table 1

[0071] Comparative experiment: Recovery of ammonia nitrogen from landfill leachate using the commonly used stripping method.

[0072] The pH of the high ammonia nitrogen wastewater was adjusted from 7-8 to 10-11, and then the ammonia nitrogen in the wastewater was removed by blowing air. The removed gas was then absorbed by the acidic absorbent liquid. The treatment effect is shown in Table 2 below.

[0073]

[0074] Table 2

[0075] As shown in Tables 1 and 2, the ammonia nitrogen recovery device of this application is superior to the ordinary stripping method in terms of treatment effect. Furthermore, the ammonia nitrogen removal effect increases with the increase of hydraulic retention time. Under the condition of fixed tank pressure and minimal changes in influent water quality, the current corresponds one-to-one with the total amount of ammonia nitrogen removed. In other words, with a fixed system current, the total amount of ammonia nitrogen removed per unit time remains constant. Therefore, with the increase of hydraulic retention time, the amount of ammonia nitrogen recovered per unit of wastewater also increases accordingly. In terms of treatment cost, the main cost of the ammonia nitrogen recovery device of this application is electricity consumption, which is approximately RMB 5.87 per kilogram of ammonia nitrogen recovered. In contrast, the main costs of ammonia nitrogen recovery by the stripping method are RMB 5.2 for alkali adjustment and RMB 3.8 for aeration, totaling RMB 9. Moreover, compared to the stripping method, the ammonia nitrogen recovery device of this application also has a certain ability to remove organic pollutants from wastewater.

[0076] Experiment 2: Using sludge digestion liquid from a wastewater treatment plant as the wastewater to be treated

[0077] The hydraulic retention time (HRT) was controlled at 25 hours, and a voltage of 0.5V was applied to both the anode and cathode assemblies for acclimatization cultivation. The potential of the anode assembly was controlled between -0.4V and -0V. Under this standard, the tank voltage was gradually increased to 7V. Once the system current stabilized, it indicated that the anode microorganisms had been successfully re-acclimatized. During actual production operation, the HRT was controlled at 10 hours, 15 hours, and 20 hours, the catholyte circulation rate in the cathode chamber was 400 L / h, and the catholyte circulation rate in the ammonia nitrogen recovery mechanism was 200 L / h. Under these conditions, the water quality indicators and ammonia nitrogen recovery in the digestate are shown in Table 3 below.

[0078]

[0079] Table 3

[0080] Comparative experiment: Experiment on the recovery of ammonia nitrogen from sludge digestion liquid using the commonly used stripping method;

[0081] The pH of the high ammonia nitrogen wastewater was adjusted from 7-8 to 10-11, and then the ammonia nitrogen in the wastewater was removed by blowing air. The removed gas was then absorbed by the acidic absorbent liquid. The treatment effect is shown in Table 4 below.

[0082]

[0083] As shown in Tables 3 and 4, the treatment of sludge digestate in this application is not significantly different from that of the stripping method. In terms of treatment cost, the main cost of this application is electricity consumption, requiring approximately 7.8 yuan per kg of ammonia nitrogen recovered. In contrast, the main costs of the stripping method for recovering ammonia nitrogen are 8.2 yuan for alkali adjustment and 4.3 yuan for aeration electricity, totaling 12.5 yuan.

[0084] In summary, compared with conventional ammonia nitrogen recovery methods, the ammonia nitrogen recovery device of this application has certain advantages in both the removal of organic pollutants in wastewater and the recovery of ammonia nitrogen.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An ammonia nitrogen recovery device, characterized in that, include: An electrodialysis apparatus includes a reaction chamber, an anode assembly, a cathode assembly, and a cation exchanger. The reaction chamber has a reaction chamber for containing waste liquid containing ammonia nitrogen. The cation exchanger is located in the reaction chamber and has a cathode chamber, a first cathode liquid inlet connector, and a first cathode liquid outlet connector, both of which are connected to the cathode chamber. The cathode assembly is located in the cathode chamber. The anode assembly includes an anode element and an electroactive microbial culture element. The anode element surrounds the cation exchanger, and the electroactive microbial culture element is located on the anode element. The electroactive microbial culture element is used to cultivate electroactive microorganisms, which decompose organic matter in the waste liquid containing ammonia nitrogen and generate electrons. An ammonia nitrogen recovery mechanism includes an ammonia nitrogen recovery mechanism body, a second cathode liquid inlet connector, a second cathode liquid outlet connector, an absorbent liquid inlet connector, and an absorbent liquid outlet connector. All four connectors are connected to the ammonia nitrogen recovery mechanism body. The second cathode liquid inlet connector is connected to the first cathode liquid outlet connector, and the second cathode liquid outlet connector is also connected to the first cathode liquid inlet connector, thus forming a cathode liquid circulation loop between the cathode chamber and the ammonia nitrogen recovery mechanism. This cathode liquid circulation loop is used to supply cathode liquid flow, and the absorbent liquid inlet connector is used to supply absorbent liquid inlet, while the absorbent liquid outlet connector is used to supply absorbent liquid outlet. When the cathode assembly and anode assembly are energized, ammonium ions in the ammonia-nitrogen-containing waste liquid enter the cathode cavity through the cation exchange element and are placed in the catholyte. The electroactive microorganisms decompose the organic matter in the ammonia-nitrogen-containing waste liquid to generate electrons. The electrons are transferred to the cathode assembly through the energizing circuit to increase the pH of the catholyte in the cathode cavity and convert the ammonium ions into free ammonia. The ammonia-nitrogen recovery mechanism is used to transfer the free ammonia to the absorbent entering the absorbent through the absorbent inlet, where it is absorbed by the catholyte and output from the absorbent outlet. The cation exchanger includes an upper cap, an upper tube, a cation exchange membrane tube, and a lower cap. The upper tube is provided with an upper tube cavity, the upper tube cap is provided at one end of the upper tube, the first cathode liquid inlet connector and the first cathode liquid outlet connector are provided on the upper tube cap, and the first cathode liquid inlet connector and the first cathode liquid outlet connector are connected to the upper tube cavity. The cation exchange membrane tube is provided with a lower cavity, and the other end of the upper tube is connected to one end of the cation exchange membrane tube. The lower tube cap is placed on the other end of the cation exchange membrane tube to close the other end of the cation exchange membrane tube. The upper cavity and the lower cavity are connected to form a cathode cavity, and the cation exchange membrane tube allows the ammonium ions to pass through. The cation exchanger also includes an inlet pipe located in the cathode cavity, one end of which is connected to a first cathode liquid inlet connector, and the other end of which extends toward the lower cap. The cathode assembly is tubular, with one end connected to the first cathode liquid outlet connector and the other end extending toward the lower cap. The cathode assembly has openings in its tube wall that allow gas and liquid to pass through.

2. The ammonia nitrogen recovery device according to claim 1, characterized in that, The cation exchanger also includes an external support tube, which is sleeved outside the cation exchange membrane tube. One end of the external support tube is fixed to the upper tube, and the other end of the external support tube is fixed to the reaction chamber. The external support tube is provided with an opening that allows the ammonia-nitrogen-containing waste liquid to pass through.

3. The ammonia nitrogen recovery device according to claim 1, characterized in that, The ammonia nitrogen recovery device also includes a transfer tank, which is provided with a transfer chamber, a third cathode liquid inlet connector, a third cathode liquid outlet connector, a fourth cathode liquid inlet connector, and a fourth cathode liquid outlet connector. The third cathode liquid inlet connector, the third cathode liquid outlet connector, the fourth cathode liquid inlet connector, and the fourth cathode liquid outlet connector are all connected to the transfer chamber. The third cathode liquid inlet connector is connected to the first cathode liquid outlet connector, the third cathode liquid outlet connector is connected to the first cathode liquid inlet connector, the fourth cathode liquid inlet connector is connected to the second cathode liquid outlet connector, and the fourth cathode liquid outlet connector is connected to the second cathode liquid inlet connector.

4. The ammonia nitrogen recovery device according to claim 3, characterized in that, The ammonia nitrogen recovery device also includes a first valve body, which is disposed on the connection between the second cathode liquid inlet connector and the ammonia nitrogen recovery mechanism body.

5. The ammonia nitrogen recovery device according to any one of claims 1-4, characterized in that, The ammonia nitrogen recovery device also includes a second valve body, which is disposed on the connection between the absorbent inlet connector and the ammonia nitrogen recovery mechanism body.

6. The ammonia nitrogen recovery device according to claim 5, characterized in that, The ammonia nitrogen recovery device also includes a pressure gauge, which is installed on the connection between the absorbent inlet and the ammonia nitrogen recovery mechanism body.

7. A method for recovering ammonia nitrogen from waste liquid, characterized in that, The method, applied to the ammonia nitrogen recovery device as described in any one of claims 1-6, comprises: Inoculate the reaction chamber with a strain containing the electroactive microorganisms; Waste liquid containing ammonia nitrogen is continuously injected into the reaction chamber, and the cathode assembly and the anode assembly are energized. When the potential of the anode assembly is within a preset potential range, the cell pressure is gradually increased. When the potential of the anode assembly is within a preset potential range and the current between the cathode assembly and the anode assembly is stable, the cathode liquid in the cathode liquid circulation loop is controlled to flow, and the absorbent is controlled to be input from the absorbent liquid inlet and output from the absorbent liquid outlet.

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