Wastewater treatment system

Abstract

To improve the treatment efficiency of wastewater treatment systems. [Solution] A wastewater treatment system according to one embodiment of the present invention is a wastewater treatment system for treating wastewater containing a sodium sulfate solution, comprising: an electrodialysis apparatus for separating the sodium sulfate solution, which is the wastewater, into a first solution containing sulfate ions, a second solution containing sodium ions, and circulating wastewater from which sodium sulfate has been removed; a first membrane distillation apparatus for extracting purified water from the first solution to concentrate the first solution; and a second membrane distillation apparatus for extracting purified water from the second solution to concentrate the second solution. This wastewater treatment system can effectively separate high-concentration ionic solutions by selectively separating salt compounds and other harmful ions in the wastewater through the electrodialysis apparatus. Through this, the recycling of materials after wastewater treatment can be maximized, and the environmental harmfulness of salt compounds can be greatly reduced.

Description

Technical Field

[0001] The present invention relates to a wastewater treatment system, and more specifically, to a closed-loop wastewater treatment system using a continuous electrodialysis and membrane distillation device.

Background Art

[0002] With the development of modern industries, the treatment and recycling of wastewater generated in various processes have emerged as important issues in terms of environmental protection and resource conservation. In particular, industrial wastewater contains various harmful components such as salt compounds, heavy metals, and organic pollutants, and technologies for effectively removing and recycling these are essential. Existing wastewater treatment technologies mainly use physical, chemical, and biological methods, and such methods often involve high costs, high energy consumption, and complex treatment processes. In particular, in the case of wastewater containing high-concentration salt compounds, it is difficult to completely remove them with existing treatment technologies, and the residual substances after treatment may have harmful effects on the environment.

[0003] Electrodialysis (ED) is a technology that separates ions by the force of an electric field using ion exchange membranes, and is mainly used for desalinating salt water or removing specific ions. This technology has advantages such as relatively low energy consumption and high selectivity. However, electrodialysis alone has limitations in removing non-volatile organic substances and fine particles in wastewater, and additional processes are required for high-concentration salt compound treatment.

[0004] Membrane distillation (MD) is a technique that uses hydrophobic membranes to concentrate and separate substances by passing them through in a vapor state. Membrane distillation can operate at low operating temperatures and is used in various application fields such as seawater desalination and concentration of high-concentration solutions. This technique has the advantages of lower energy consumption and less fouling compared to existing heat source-based processes. However, membrane distillation processes have disadvantages, such as the possibility of reduced efficiency when using new renewable energy or waste heat as a heat source, and the fact that processing efficiency can vary depending on climatic conditions.

[0005] Therefore, focusing on the aforementioned problems, the present invention presents a closed-loop wastewater treatment system utilizing a continuous electrodialysis-membrane distillation apparatus that overcomes the limitations of existing wastewater treatment technologies and offers a more economical and environmentally friendly wastewater treatment and catalyst recycling method. This system should be able to effectively treat wastewater generated in various industrial fields, increase the possibility of recycling, and make an important contribution in terms of environmental protection and resource conservation. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Korean Registered Patent Publication No. 10-2217405 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention aims to solve the above-mentioned problems by improving the treatment efficiency of a wastewater treatment system by constructing a closed-circulation system using an electrodialysis apparatus and a membrane distillation apparatus.

[0008] Furthermore, its purpose is to construct a closed-loop wastewater reuse and catalyst recovery system that separates, purifies, concentrates, and recycles salt compounds generated during the compound production process. [Means for solving the problem]

[0009] A wastewater treatment system according to one embodiment of the present invention is a wastewater treatment system for treating wastewater containing a sodium sulfate solution, and includes an electrodialysis apparatus for separating the sodium sulfate solution, which is the wastewater, into a first solution containing sulfate ions, a second solution containing sodium ions, and circulating wastewater from which sodium sulfate has been removed; a first membrane distillation apparatus for extracting purified water from the first solution to concentrate the first solution; and a second membrane distillation apparatus for extracting purified water from the second solution to concentrate the second solution.

[0010] A wastewater treatment system according to one embodiment of the present invention includes a wastewater tank in which the wastewater is stored, and the circulating wastewater can enter the wastewater tank.

[0011] A wastewater treatment system according to one embodiment of the present invention may include a cooling water tank formed by the confluence and cooling of purified water extracted from the first membrane distillation apparatus and the second membrane distillation apparatus.

[0012] In a wastewater treatment system according to one embodiment of the present invention, the first membrane distillation apparatus includes a first membrane distillation tank, and the first membrane distillation tank is divided into a first solution concentration space into which the first solution enters and a first cooling space into which the cooling water enters, and includes a first hydrophobic dialysis membrane through which distilled water extracted from the first solution passes in the form of water vapor. The second membrane distillation apparatus may also include a second membrane distillation tank, and the second membrane distillation tank is divided into a second solution concentration space into which the second solution enters and a second cooling space into which the cooling water enters, and includes a second hydrophobic dialysis membrane through which distilled water extracted from the second solution passes in the form of water vapor.

[0013] A wastewater treatment system according to one embodiment of the present invention includes a first solution concentration tank into which the first solution extracted from the first solution concentration space enters, and a second solution concentration tank into which the second solution extracted from the second solution concentration space enters. The first solution may be concentrated by entering the first solution concentration space again from the first solution concentration tank, and the second solution may be concentrated by entering the second solution concentration space again from the second solution concentration tank.

[0014] In a wastewater treatment system according to one embodiment of the present invention, the electrodialysis apparatus may include an electrodialysis tank, a positive electrode formed on one side of the electrodialysis tank, a negative electrode formed on the other side of the electrodialysis tank, two bipolar membranes formed adjacent to the positive electrode and the negative electrode, an anion dialysis membrane formed opposite to the bipolar membranes and closer to the positive electrode, a cation dialysis membrane formed opposite to the bipolar membranes and closer to the negative electrode, a central space into which the wastewater enters, a first solution formation space separated by the cation dialysis membrane and the anion dialysis membrane, in which a sodium sulfate solution is electrolyzed in the central space and sulfate ions pass through the anion dialysis membrane to form a first solution, and a second solution formation space separated by the bipolar membrane and the cation dialysis membrane, in which a sodium sulfate solution is electrolyzed in the central space and sodium ions pass through the cation dialysis membrane to form a second solution.

[0015] In the wastewater treatment system according to one embodiment of the present invention, the cooling water may be supplied to the first solution forming space and the second solution forming space.

[0016] A wastewater treatment system according to one embodiment of the present invention may include a first solution confluence point where a first solution from the first solution concentration tank and a first solution from the first solution formation space merge with each other, a first heater formed between the first solution confluence point and the first solution concentration space, a second solution confluence point where a second solution from the second solution concentration tank and a second solution from the second solution formation space merge with each other, and a second heater formed between the second solution confluence point and the second solution concentration space.

[0017] A wastewater treatment system according to one embodiment of the present invention may include a first cooler for cooling the cooling water entering the first cooling space, and a second cooler for cooling the cooling water entering the second cooling space.

[0018] In the wastewater treatment system according to one embodiment of the present invention, the first solution may be formed into an acidic aqueous solution containing sulfate ions in the first solution formation space, and the second solution may be formed into an aqueous hydroxide solution containing sodium ions in the second solution formation space. [Effects of the Invention]

[0019] A wastewater treatment system according to one embodiment of the present invention can effectively separate high-concentration ionic solutions by selectively separating salt compounds and other harmful ions in wastewater through an electrodialysis device. Through this, the recycling of materials after wastewater treatment can be maximized, and the environmental harmfulness of salt compounds can be greatly reduced.

[0020] Furthermore, the use of membrane distillation equipment allows for the effective concentration of ionic solutions separated through electrodialysis. In particular, it can operate at low operating temperatures, minimizing energy consumption and reducing costs by utilizing renewable energy and waste heat. This contributes to increasing the production efficiency of treated water in the membrane distillation process.

[0021] In addition, the wastewater treatment system of the present invention adopts a closed-loop structure, and the treated water can be reused or utilized in various industrial applications. Through this, it is possible to promote resource recycling, reduce the costs for wastewater treatment, and contribute to sustainable environmental protection.

Brief Description of the Drawings

[0022] [Figure 1] It is a schematic diagram of a wastewater treatment system according to an embodiment of the present invention. [Figure 2] It is a schematic diagram of an electrodialysis device of a wastewater treatment system according to an embodiment of the present invention. [Figure 3] It is a schematic diagram of a first membrane distillation device of a wastewater treatment system according to an embodiment of the present invention. [Figure 4] It is a schematic diagram of a second membrane distillation device of a wastewater treatment system according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0023] Hereinafter, various embodiments of the present invention will be described with reference to the accompanying drawings. The present invention is not limited to specific embodiments and should be understood to include various modifications, equivalents, and / or alternatives of the embodiments of the present invention. In connection with the description of the drawings, similar reference numerals may be used for similar components.

[0024] In this specification, expressions such as "having", "being able to have", "including", or "being able to include" refer to the presence of the feature (e.g., a component such as a numerical value, function, operation, or part), and do not exclude the presence of additional features.

[0025] In this specification, expressions such as “A or B,” “A or / and at least one of B,” or “one or more of A or / and B” can include all possible combinations of the items listed together. For example, “A or B,” “A and at least one of B,” or “at least one of A or B” can refer to all cases where (1) at least one A is included, (2) at least one B is included, or (3) at least one A and at least one B are all included.

[0026] As used herein, the expression "configured to" may be replaced, depending on the context, with other expressions such as "suitable for," "having the capacity to," "designed to," "adapted to," "made to," or "capable of." The term "configured to" does not necessarily mean "specifically designed to."

[0027] The terms used herein are used solely to describe specific embodiments and are not intended to limit the scope of other embodiments. Singular expressions may include plural expressions unless the context clearly indicates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as those generally understood by those ordinary skill in the art described herein. Terms used herein that are defined in general dictionaries may be interpreted as having the same or similar meaning as they do in the context of the relevant technology, and not as ideally or excessively formal unless explicitly defined herein. Where applicable, terms defined herein should not be construed to exclude the embodiments described herein.

[0028] Therefore, it should be understood that the configurations of the embodiments described herein represent only some of the most preferred embodiments of the present invention and do not represent the entire technical concept of the present invention, and that there may be various equivalents and modifications that can be substituted therein at the time of filing this application.

[0029] When a specification as a whole states that a certain part "includes" a certain component, unless otherwise specified, this means that it may include other components rather than excluding them.

[0030] The objects, particular advantages, and novel features of the present invention described herein will become even clearer from the accompanying drawings, the following detailed description, and preferred embodiments. It should be noted that, in assigning reference numerals to components in each drawing herein, the same component is assigned the same number whenever possible, even if it appears in other drawings. Furthermore, terms such as “one side,” “other side,” “first,” and “second” are used to distinguish one component from another, and the components are not limited by such terms. In describing the present invention, detailed descriptions of related prior art that could unnecessarily obscure the gist of the invention are omitted below.

[0031] Hereinafter, an embodiment of the present invention will be described in detail with reference to the attached drawings, where the same reference numerals indicate the same components.

[0032] The wastewater treatment system 1 according to the present invention will be described below with reference to the drawings.

[0033] Figure 1 is a schematic diagram of a wastewater treatment system 1 according to one embodiment of the present invention.

[0034] A wastewater treatment system 1 according to one embodiment of the present invention is a wastewater treatment system 1 for treating wastewater P containing a sodium sulfate solution, and includes an electrodialysis apparatus 10 for separating the sodium sulfate solution of the wastewater P into a first solution C1 containing sulfate ions, a second solution C2 containing sodium ions, and circulating wastewater P1 from which the sodium sulfate has been removed; a first membrane distillation apparatus 20 for extracting purified water W from the first solution C1 to concentrate the first solution C1; and a second membrane distillation apparatus 30 for extracting purified water W from the second solution C2 to concentrate the second solution C2.

[0035] A wastewater treatment system 1 according to one embodiment of the present invention may specifically relate to a closed-loop wastewater reuse and catalyst recovery system that treats and recycles wastewater generated in the depolymerization process of polyethylene terephthalate (PET). PET is a polymer widely used in the manufacture of various products such as fibers, bottles, and films, and sodium hydroxide (NaOH) and sulfuric acid (H2SO4) are mainly used in the depolymerization process. The wastewater generated in this process comes to contain various compounds such as sodium sulfate (Na2SO4), and since such compounds can be harmful to the environment, appropriate treatment is necessary.

[0036] In the depolymerization process of PET, sodium hydroxide (NaOH) is used to hydrolyze ester bonds to produce ethylene glycol (EG) and terephthalic acid (TPA). In this process, sodium hydroxide is converted to sodium terephthalate (Na2TP), and then sulfuric acid (H2SO4) is added to recover the terephthalic acid, followed by sodium sulfate (N2TP). a2 It forms SO4. Such wastewater contains high concentrations of salts such as sodium sulfate and requires purification and concentration before being released into the environment.

[0037] As shown in Figure 1, a wastewater treatment system 1 according to one embodiment of the present invention includes an electrodialysis apparatus 10, a first membrane distillation apparatus 20, and a second membrane distillation apparatus 30.

[0038] A wastewater treatment system 1 according to one embodiment of the present invention is for treating wastewater P containing a sodium sulfate solution, wherein the wastewater P first enters an electrodialysis apparatus 10 for treatment. The electrodialysis apparatus 10 separates the wastewater P containing the sodium sulfate solution into a first solution C1 containing sulfate ions, a second solution C2 containing sodium ions, and circulating wastewater P1 from which the sodium sulfate has been removed.

[0039] The first membrane distillation apparatus 20 is a device that concentrates the first solution C1 by heating the first solution C1 and extracting purified water as steam.

[0040] The second membrane distillation apparatus 30 is a device that concentrates the second solution C2 by heating the second solution C2 and extracting purified water as steam.

[0041] A wastewater treatment system 1 according to one embodiment of the present invention includes a wastewater tank 60 in which the wastewater P is stored, and the circulating wastewater P1 can enter the wastewater tank 60.

[0042] In a wastewater treatment system 1 according to one embodiment of the present invention, the wastewater tank 60 is a tank in which wastewater P is stored. The wastewater P stored in the wastewater tank 60 enters the electrodialysis machine 10. Here, the circulating wastewater P1 from which sodium sulfate has been removed in the electrodialysis machine 10 enters the wastewater tank 60 again. Therefore, sodium sulfate that could not be completely removed from the circulating wastewater P1 can be returned to the electrodialysis machine 10, thereby maximizing the efficiency of the system 1 by creating a closed circulation of wastewater.

[0043] A wastewater treatment system 1 according to one embodiment of the present invention may include a cooling water tank 70 for which purified water W extracted from the first membrane distillation apparatus 20 and the second membrane distillation apparatus 30 is combined and cooled to form cooling water W1.

[0044] The cooling water tank 70 is formed for the purpose of circulating the cooling water W1 in system 1. Purified water W extracted from the first membrane distillation apparatus 20 and the second membrane distillation apparatus 30 are combined into the cooling water tank 70. In the cooling water tank 70, the purified water W is collected and stored as cooling water W1.

[0045] In a wastewater treatment system 1 according to one embodiment of the present invention, the first membrane distillation apparatus 20 includes a first membrane distillation tank 21, and the first membrane distillation tank 21 is divided into a first solution concentration space 23 into which the first solution C1 enters and a first cooling space 24 into which the cooling water W1 enters, and includes a first hydrophobic dialysis membrane 22 through which distilled water extracted from the first solution C1 passes in the form of water vapor. The second membrane distillation apparatus 30 includes a second membrane distillation tank 31, and the second membrane distillation tank 31 is divided into a second solution concentration space 33 into which the second solution C2 enters and a second cooling space 34 into which the cooling water W1 enters, and includes a second hydrophobic dialysis membrane 32 through which distilled water extracted from the second solution C2 passes in the form of water vapor.

[0046] Figure 3 shows the first membrane distillation apparatus 20. The first membrane distillation apparatus 20 may include a first membrane distillation tank 21, a first hydrophobic dialysis membrane 22, a first solution concentration space 23, and a first cooling space 24.

[0047] The first membrane distillation tank 21 constitutes the frame of the first membrane distillation apparatus 20.

[0048] The first hydrophobic dialysis membrane 22 divides the internal space of the first membrane distillation tank 21 into a first solution concentration space 23 and a first cooling space 24. The first solution C1 enters the first solution concentration space 23, and the first solution C1 is supplied in a heated state to facilitate the generation of steam. The steam generated from the first solution C1 moves to the first cooling space 24 via the first hydrophobic dialysis membrane 22. Cooled cooling water W1 enters the first cooling space 24, helping to condense the steam and convert it into purified water W.

[0049] Figure 4 shows the second membrane distillation apparatus 30. The second membrane distillation apparatus 30 may include a second membrane distillation tank 31, a second hydrophobic dialysis membrane 32, a second solution concentration space 33, and a second cooling space 34.

[0050] The second membrane distillation tank 31 constitutes the frame (housing) of the second membrane distillation apparatus 30.

[0051] The second hydrophobic dialysis membrane 32 divides the internal space of the second membrane distillation tank 31 into a second solution concentration space 33 and a second cooling space 34. The second solution C2 enters the second solution concentration space 33, and the second solution C2 is supplied in a heated state to facilitate the generation of steam. The steam generated from the second solution C2 moves to the second cooling space 34 via the second hydrophobic dialysis membrane 32. Cooled cooling water W1 enters the second cooling space 34, helping to condense the steam and convert it into purified water W.

[0052] A wastewater treatment system 1 according to one embodiment of the present invention includes a first solution concentration tank 40 into which the first solution C1 extracted from the first solution concentration space 23 enters, and a second solution concentration tank 50 into which the second solution C2 extracted from the second solution concentration space 33 enters. The first solution C1 can be concentrated by entering the first solution concentration space 23 again from the first solution concentration tank 40, and the second solution C2 can be concentrated by entering the second solution concentration space 33 again from the second solution concentration tank 50.

[0053] As can be seen in Figure 1, the first solution C1 concentrated in the first membrane distillation apparatus 20 is continuously concentrated through circulation. For this purpose, a first solution concentration tank 40 is formed where the first solution C1 extracted from the first solution concentration space 23 is collected. The first solution concentration tank 40 may also be equipped with a first solution concentration measuring sensor for measuring the concentration of the first solution C1. Therefore, when the first solution C1 in the first solution concentration tank 40 reaches a concentration above a certain level, the control unit of system 1 can remove the first solution C1 to the outside. When the concentration of the first solution C1 in the first solution concentration tank 40 is formed to be below the target concentration, the first solution C1 can be allowed to enter the first solution concentration space 23 again, thereby continuing the continuous and cyclical concentration activity.

[0054] As can be seen in Figure 2, the second solution C2 concentrated in the second membrane distillation apparatus 30 is continuously concentrated through circulation. For this purpose, a second solution concentration tank 50 is formed where the second solution C2 extracted from the second solution concentration space 33 is collected. The second solution concentration tank 50 may be further equipped with a second solution concentration measuring sensor for measuring the concentration of the second solution C2. Therefore, when the second solution C2 in the second solution concentration tank 50 reaches a concentration above a certain level, the control unit of system 1 can remove the second solution C2 to the outside. When the concentration of the second solution C2 in the second solution concentration tank 50 is formed to be below the target concentration, the second solution C2 can be allowed to enter the second solution concentration space 33 again, thereby continuing the continuous and cyclical concentration activity.

[0055] In a wastewater treatment system 1 according to one embodiment of the present invention, the electrodialysis apparatus 10 comprises an electrodialysis tank 11, a positive electrode 12 formed on one side of the electrodialysis tank 11, a negative electrode 13 formed on the other side of the electrodialysis tank 11, two bipolar membranes 14 formed adjacent to the positive electrode 12 and the negative electrode 13, an anion dialysis membrane 15 formed opposite to one of the bipolar membranes 14 and closer to the positive electrode, a cation dialysis membrane 16 formed opposite to the other bipolar membrane 14 and closer to the negative electrode, and a space separated between the cation dialysis membrane 16 and the anion dialysis membrane 15. The system may include a central space 17 into which the wastewater P enters, a space separated between one of the bipolar membranes 14 and the anion dialysis membrane 15, a first solution formation space 18 in which sulfate ions formed by the electrolysis of sodium sulfate solution in the central space 17 pass through the anion dialysis membrane 15 to form a first solution C1, and a space separated between the other bipolar membrane 14 and the cation dialysis membrane 16, a second solution formation space 19 in which sodium ions formed by the electrolysis of sodium sulfate solution in the central space 17 pass through the cation dialysis membrane 16 to form a second solution C2.

[0056] In one embodiment of the present invention, the wastewater treatment system 1 can form the first solution C1 into an acidic aqueous solution containing sulfate ions in the first solution formation space 18, and form the second solution C2 into an aqueous hydroxide solution containing sodium ions in the second solution formation space 19.

[0057] The electrodialysis apparatus 10 of the wastewater treatment system 1 according to one embodiment of the present invention forms an electric field between a positive electrode 12 and a negative electrode 13 to promote ion movement. The electrodialysis tank 11 forms the frame (housing) of the electrodialysis apparatus 10. Here, a positive electrode 12 and a negative electrode 13 are formed on one side and the other side of the electrodialysis tank 11, respectively. Two bipolar membranes 14 are formed adjacent to the positive electrode 12 and the negative electrode 13, and these bipolar membranes 14 each contain hydrogen ions (H + ) and hydroxide ions (OH -The anion dialysis membrane 15 plays the role of generating sulfate ions (SO4), which are anions. 2- The cation dialysis membrane 16 moves the sodium ion (Na), which is a cation. + Move ).

[0058] Inside the electrodialysis apparatus 10, an electric field is formed between the positive electrode 12 and the negative electrode 13 to promote ion movement. Due to the influence of the electric field, hydrogen ions move toward the negative electrode 13, and hydroxide ions move toward the positive electrode 12. Sulfate ions move through the anion dialysis membrane 15 to the first solution formation space 18 where the first solution C1 is formed, and ion exchange takes place. Sodium ions move through the cation dialysis membrane 16 to the second solution formation space 19 where the second solution C2 is formed, and ion exchange takes place.

[0059] In this process, the bipolar membrane 14 electrolyzes water to produce hydrogen ions and hydroxide ions, while the anion dialysis membrane 15 and the cationic dialysis membrane 16 are responsible for the movement of anions and cations, respectively, assisting in the separation of electrolytes.

[0060] The central space 17 is a space from which sodium sulfate is removed from wastewater P. The circulating wastewater P1 that exits the central space 17, with a certain amount of sodium sulfate removed, enters the wastewater tank 60 again and circulates within the system 1.

[0061] In the wastewater treatment system 1 according to one embodiment of the present invention, the cooling water W1 can be supplied to the first solution forming space 18 and the second solution forming space 19.

[0062] As can be seen in Figure 1, the cooling water W1 stored in the cooling water tank 70 also enters the first solution formation space 18 and the second solution formation space 19. Therefore, by continuously supplying water from the cooling water tank 70, the first solution C1 and the second solution C2 can be extracted from the electrodialysis apparatus 10 without the need for additional water supply within System 1.

[0063] A wastewater treatment system 1 according to one embodiment of the present invention may include a first solution confluence point 101 where the first solution C1 from the first solution concentration tank 40 and the first solution C1 from the first solution forming space 18 merge with each other, a first heater 103 formed between the first solution confluence point 101 and the first solution concentration space 23, a second solution confluence point 102 where the second solution C2 from the second solution concentration tank 50 and the second solution C2 from the second solution forming space 19 merge with each other, and a second heater 104 formed between the second solution confluence point 102 and the second solution concentration space 33.

[0064] As shown in Figure 1, the wastewater treatment system 1 according to one embodiment of the present invention may further include a first solution confluence point 101, a second solution confluence point 102, a first heater 103, and a second heater 104.

[0065] The first solution confluence point 101 is the point where the first solution C1 newly created in the first solution formation space 18 and the existing first solution C1 in the circulating first solution concentration tank 40 merge. The first heater 103 is formed between the first solution confluence point 101 and the first solution concentration space 23, allowing the first solution C1 to be heated all at once, thereby ensuring that the distillation activity in the first membrane distillation apparatus 20 proceeds smoothly.

[0066] The second solution confluence point 102 is the point where the second solution C2 newly produced in the second solution formation space 19 and the existing second solution C2 in the circulating second solution concentration tank 50 merge. The second heater 104 is formed between the second solution confluence point 102 and the second solution concentration space 33, allowing the second solution C2 to be heated all at once, thereby facilitating the distillation activity within the second membrane distillation apparatus 30.

[0067] A wastewater treatment system 1 according to one embodiment of the present invention may include a first cooler 105 for cooling the cooling water W1 entering the first cooling space 24, and a second cooler 106 for cooling the cooling water W1 entering the second cooling space 34.

[0068] As shown in Figure 1, the first cooler 105 cools the cooling water W1 that enters the first cooling space 24, thereby cooling the distilled water vapor in the first cooling space.

[0069] Similarly, the second cooler 106 cools the cooling water W1 that enters the second cooling space 34, thereby cooling the distilled water vapor in the second cooling space.

[0070] A wastewater treatment system 1 according to one embodiment of the present invention enables the recycling of sodium hydroxide and sulfuric acid recovered after wastewater treatment as catalysts. The recovered sodium hydroxide is used in the PET depolymerization process, and the sulfuric acid is reused to convert sodium terephthalate to terephthalic acid.

[0071] Although the present invention has been described in detail through specific embodiments, this is merely for the purpose of illustrating the present invention, and it is clear that the present invention is not limited thereto, and that modifications and improvements can be made within the technical concept of the present invention by those with ordinary skill in the art.

[0072] Any mere modification or alteration of the present invention falls within the scope of the present invention, and the specific scope of protection of the present invention will be clarified by the appended claims. [Explanation of symbols]

[0073] P: Wastewater, P1: Recirculating wastewater, C1: First solution, C2: Second solution, W: Purified water, W1: Cooling water, 1: Wastewater treatment system, 10: Electrodialysis machine, 11: Electrodialysis tank, 12: Positive electrode, 13: Negative electrode, 14: Bipolar membrane, 15: Anion dialysis membrane, 16: Cation dialysis membrane, 17: Central space, 18: First solution formation space, 19: Second solution formation space, 20: First membrane distillation apparatus, 21: First membrane distillation tank, 22: First hydrophobic dialysis membrane, 23: First Solution concentration space, 24: First cooling space, 30: Second membrane distillation apparatus, 31: Second membrane distillation tank, 32: Second hydrophobic dialysis membrane, 33: Second solution concentration space, 34: Second cooling space, 40: First solution concentration tank, 50: Second solution concentration tank, 60: Wastewater tank, 70: Cooling water tank, 101: First solution confluence point, 102: Second solution confluence point, 103: First heater, 104: Second heater, 105: First cooler, 106: Second cooler, 107: Pump

Claims

1. A wastewater treatment system for treating wastewater containing a sodium sulfate solution, An electrodialysis apparatus for separating the wastewater into a first solution containing sulfate ions, a second solution containing sodium ions, and circulating wastewater from which sodium sulfate has been removed. A first membrane distillation apparatus for extracting purified water from the first solution in order to concentrate the first solution, A second membrane distillation apparatus for extracting purified water from the second solution in order to concentrate the second solution, A wastewater tank into which the wastewater is stored and into which the circulating wastewater enters, A cooling water tank for cooling water, formed by combining and cooling the purified water extracted from the first membrane distillation apparatus and the second membrane distillation apparatus, Includes, The first membrane distillation apparatus is First membrane distillation tank, The first membrane distillation tank is divided into two parts: a first solution concentration space into which the first solution enters, and a first cooling space into which the cooling water enters, and a first hydrophobic dialysis membrane through which the distilled water extracted from the first solution passes in the form of water vapor, Includes, The second membrane distillation apparatus is The second membrane distillation tank, The second membrane distillation tank is divided into a second solution concentration space into which the second solution enters, and a second cooling space into which the cooling water enters, and a second hydrophobic dialysis membrane through which the distilled water extracted from the second solution passes in the form of water vapor, Includes, The aforementioned wastewater treatment system is A first solution concentration tank into which the first solution extracted from the first solution concentration space enters, The system further includes a second solution concentration tank into which the second solution extracted from the second solution concentration space enters, The first solution is concentrated again when it enters the first solution concentration space from the first solution concentration tank. The second solution is concentrated again when it enters the second solution concentration space from the second solution concentration tank. The wastewater treatment system further includes a control unit, which is: When the concentration of the first solution in the first solution concentration tank reaches a certain level or higher, the first solution is removed to the outside, and when the concentration of the first solution in the first solution concentration tank reaches a target level or lower, the first solution in the first solution concentration tank is allowed to enter the first solution concentration space. When the concentration of the second solution in the second solution concentration tank reaches a certain level or higher, the second solution is removed to the outside, and when the concentration of the second solution in the second solution concentration tank reaches a target level or lower, the second solution in the second solution concentration tank is allowed to enter the second solution concentration space. The electrodialysis apparatus is, Electrodialysis tank and A positive electrode formed on one side of the electrodialysis tank, The negative electrode formed on the other side of the electrodialysis tank, Two bipolar films are formed adjacent to the positive electrode and the negative electrode, respectively. An anion dialysis membrane is formed opposite to the bipolar membrane and is formed closer to the positive electrode, A cation dialysis membrane is formed opposite the other bipolar membrane and is formed closer to the negative electrode, A space separated by the cation dialysis membrane and the anion dialysis membrane, comprising a central space into which the wastewater enters, A space separated by the one bipolar membrane and the anion dialysis membrane, wherein sulfate ions formed by the electrolysis of a sodium sulfate solution in the central space pass through the anion dialysis membrane to form a first solution, and a first solution formation space, A space separated by the other bipolar membrane and the cation dialysis membrane, wherein sodium ions formed by the electrolysis of a sodium sulfate solution in the central space pass through the cation dialysis membrane to form a second solution, and a second solution formation space, Includes, The cooling water is supplied to the first solution forming space and the second solution forming space. The aforementioned wastewater treatment system is A first solution confluence point where the first solution from the first solution concentration tank and the first solution from the first solution formation space merge with each other, A first heater is formed between the first solution confluence point and the first solution concentration space, A second solution confluence point where the second solution from the second solution concentration tank and the second solution from the second solution formation space merge with each other, A second heater is formed between the second solution confluence point and the second solution concentration space, A wastewater treatment system, which further includes this.

2. A first cooler for cooling the cooling water entering the first cooling space, The wastewater treatment system according to claim 1, further comprising a second cooler for cooling the cooling water that enters the second cooling space.

3. In the first solution forming space, the first solution is formed into an acidic aqueous solution containing sulfate ions. The wastewater treatment system according to claim 2, wherein the second solution is formed in the second solution formation space into an aqueous hydroxide solution containing sodium ions.

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