A zero-discharge treatment system for refined wastewater of para-aramid fiber

Abstract

The utility model relates to a kind of zero discharge treatment systems of aramid refining wastewater for protection, crystallization sedimentation tank, softening clarifier, multi-medium filter, electro-catalytic oxidation device, activated carbon filter, ultrafiltration device, primary nanofiltration device, secondary nanofiltration device, high-salt reverse osmosis device and MVR evaporation crystallization device are sequentially communicated, the concentrated water produced by primary nanofiltration device is backflowed into crystallization sedimentation tank, and the concentrated water produced by secondary nanofiltration device is backflowed into the water inlet of ultrafiltration device;Crystallization sedimentation tank is equipped with calcium chloride solution dosing device;Softening clarifier is equipped with sodium carbonate solution dosing device, NaOH dosing device, PFS dosing device, PAM dosing device and concentrated sulfuric acid dosing device.Affirmative effect is: through scientific research, combination is effective treatment process, its operation is stable and reliable, effectively removes sulfate and hardness in wastewater, reduces divalent ion content in water, effectively removes organic matter in water.

Description

Technical Field

[0001] This utility model relates to the field of wastewater treatment, specifically to a zero-discharge treatment system for protective para-aramid refining wastewater. Background Technology

[0002] Para-aramid, officially known as poly(p-phenylene terephthalamide) fiber, abbreviated as PPTA, is a special high-performance fiber material with excellent mechanical properties, stable chemical properties, and ideal mechanical properties. Its most prominent properties are high strength and high modulus. It also possesses outstanding thermal properties such as low density, wear resistance, impact resistance, fatigue resistance, low expansion, low thermal conductivity, non-flammability, non-melting, and excellent shock absorption, as well as excellent dielectric properties. The combination of para-aramid's impact resistance and the high tensile strength of carbon fiber makes it an effective advanced composite material. Its filament fiber material can be processed into ropes or nets in the first step, and then processed into curtain fabric, conveyor belts, bulletproof vests, or protective equipment in the second step. It is playing an increasingly important role in the upgrading of pillar industries in developed countries and in improving the overall quality of the national economy. It also has significant implications for the adjustment of my country's industrial structure and the upgrading of traditional materials.

[0003] The production of para-aramid fibers generates several types of wastewater, one of which is refining wastewater. This wastewater is characterized by high salt content, high hardness, and relatively high COD concentration, making it very difficult to treat. Traditional biological treatment processes are inhibited by the high salt content and cannot remove the salt. COD removal becomes a problem. Typical reverse osmosis processes are affected by high hardness and high COD content, leading to membrane system fouling, short membrane element life, and limitations imposed by high salt content. Generally, reverse osmosis processes have low water recovery rates and poor economic efficiency. At the same time, they also lead to an increase in the scale of subsequent evaporation and crystallization, resulting in low-quality crystalline salt and a surge in engineering investment and operating costs.

[0004] Currently, China faces a severe environmental situation, making energy conservation and emission reduction an urgent necessity. Effective and economical treatment of the refining wastewater generated during the production of protective para-aramid fibers is in line with national needs. Utility Model Content

[0005] The technical problem to be solved by this utility model is to provide a zero-discharge treatment system for protective para-aramid refining wastewater, so as to overcome the shortcomings of the prior art.

[0006] The technical solution of this utility model to solve the above-mentioned technical problems is as follows: A zero-discharge treatment system for wastewater from the refining of para-aramid fibers for protection includes: a crystallization sedimentation tank, a softening and clarification tank, a multi-media filter, an electrocatalytic oxidation device, an activated carbon filter, an ultrafiltration device, a primary nanofiltration device, a secondary nanofiltration device, a high-salt reverse osmosis device, and an MVR evaporation and crystallization device. The crystallization sedimentation tank, softening and clarification tank, multi-media filter, electrocatalytic oxidation device, activated carbon filter, ultrafiltration device, primary nanofiltration device, secondary nanofiltration device, high-salt reverse osmosis device, and MVR evaporation and crystallization device are sequentially connected. The concentrated water produced by the primary nanofiltration device is returned to the crystallization sedimentation tank, and the concentrated water produced by the secondary nanofiltration device is returned to the inlet of the ultrafiltration device. The crystallization sedimentation tank is equipped with a calcium chloride solution dosing device; the softening and clarification tank is equipped with a sodium carbonate solution dosing device, a NaOH dosing device, a PFS dosing device, a PAM dosing device, and a concentrated sulfuric acid dosing device.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, the calcium chloride solution dosing device is used to add a calcium chloride solution with a concentration of 40%.

[0009] Furthermore, the sodium carbonate solution dosing device is used to add a 10% sodium carbonate solution.

[0010] Furthermore, the multi-media filter uses quartz sand and anthracite as fillers, with filling heights of 800mm and 400mm respectively; the quartz sand has a particle size of 0.5mm to 1.2mm and a non-uniformity coefficient K80 < 2.0; the anthracite has a particle size of 0.8mm to 1.8mm and a non-uniformity coefficient K80 < 1.7.

[0011] Furthermore, the electrocatalytic oxidation device is equipped with a circulating reflux pump and a waste gas treatment device.

[0012] Furthermore, the filter media for the activated carbon filter consists of quartz sand and activated carbon, with filling heights of 200mm and 1500mm respectively; the quartz sand has a particle size of 1.0mm to 2.0mm and a non-uniformity coefficient K80 < 2.0; the activated carbon has a particle size of 8 mesh to 16 mesh and a non-uniformity coefficient K80 < 1.7.

[0013] Furthermore, the membrane element selected for the ultrafiltration device is an external pressure ultrafiltration membrane, the ultrafiltration device is equipped with a cross-flow operation pipeline, a self-cleaning filter is installed in the front section of the ultrafiltration device, and the ultrafiltration device is equipped with a backwashing system.

[0014] Furthermore, the first-stage nanofiltration unit adopts a two-stage structure and is equipped with an inter-stage booster pump; the first-stage nanofiltration unit is equipped with a security filter with a filtration accuracy of 5μm at the front end; the first-stage nanofiltration unit is equipped with a non-oxidizing bactericide dosing device, a hydrochloric acid dosing device, a reducing agent dosing device, and a scale inhibitor dosing device; the dosing method of the non-oxidizing bactericide dosing device is shock dosing.

[0015] Furthermore, the secondary nanofiltration unit adopts a three-section structure. The front section of the secondary nanofiltration unit is equipped with a security filter with a filtration accuracy of 5μm. The secondary nanofiltration unit is equipped with a non-oxidizing bactericide dosing device and a scale inhibitor dosing device. The dosing method of the non-oxidizing bactericide dosing device is shock dosing.

[0016] Furthermore, the permeate from the high-salt reverse osmosis unit enters the recycled water pool; the condensate produced in the MVR evaporation crystallization unit also enters the recycled water pool.

[0017] The beneficial effects of this utility model are: 1. Based on the characteristics of the wastewater and the analysis of the raw materials used in the enterprise's production, the reagents added in the crystallization sedimentation tank and softening clarification tank stages are all reagents required for the enterprise's production, and are readily available and economical. The crystallization sedimentation tank can accept and treat the concentrated water generated by the subsequent first-stage nanofiltration unit, and the softening clarification tank can accept and treat various flushing water, backwash water, cleaning water, and sludge removal water generated in the entire process system, so that no additional wastewater is generated in the system, which plays an important role in achieving the goal of zero discharge. This stage can remove a large amount of sulfate and hardness, greatly reducing the risk of scaling and fouling of the subsequent membrane system, ensuring the safe and stable operation of the membrane system, and extending the service life of the membrane elements. At the same time, the calcium sulfate dihydrate sludge produced can be made into gypsum, which has certain economic benefits. 2. Suspended solids in the effluent from the softening and clarification tank are removed using a multi-media filter. The filter media is inexpensive and has a significant treatment effect, effectively preventing fouling of subsequent process equipment. The electrocatalytic oxidation device, combined with the activated carbon filter, effectively removes organic pollutants from the water, greatly reducing the risk of biofouling in the subsequent membrane system, improving the recovery rate of the membrane device, and reducing the scale of the evaporation and crystallization system. This series of pretreatment measures plays a very effective protective role for the subsequent membrane system, ensuring the long-term safe and stable operation of the membrane system, significantly extending the service life of the membrane elements, effectively reducing investment and operating costs, and ensuring the quality of the reclaimed water and sodium chloride crystals. 3. The combination of process units in the entire process system is economical and reasonable, with a high degree of automation, stable operation, and low labor intensity. It has a significant effect on the treatment of refined wastewater with high salt content, high hardness, and high COD concentration generated during the production of para-aramid for protective purposes. The quality of the recycled water and sodium chloride crystal salt produced is stable. The entire process system has no wastewater discharge, achieving the goal of zero discharge. It not only solves the environmental protection problem of enterprises, but also turns waste into treasure. It has very good environmental, social and economic benefits, especially for enterprises located in areas with scarce water resources and high environmental protection and energy conservation requirements. 4. Addressing the characteristics of refining wastewater generated during the production of protective para-aramid fibers, a set of effective treatment processes has been developed through scientific research. This process is stable and reliable, effectively removing sulfate and hardness from the wastewater, reducing the content of divalent ions, effectively removing organic matter, protecting the membrane system's stable operation, improving membrane system recovery rate, reducing the scale and investment of the evaporation system, and improving the quality of sodium chloride industrial salt and reclaimed water. Furthermore, the generated calcium sulfate dihydrate sludge can be used to produce gypsum, offering certain economic benefits. This process effectively treats the refining wastewater generated during the production of protective para-aramid fibers, achieving zero discharge targets, while also producing qualified reclaimed water required for the company's production. Simultaneously, it produces high-quality sodium chloride industrial salt and gypsum, demonstrating good environmental and economic benefits. The entire process system has a high degree of automation, effectively reducing labor intensity. Attached Figure Description

[0018] Figure 1 This is a structural diagram of the zero-discharge treatment system for para-aramid refining wastewater for protective purposes in this utility model.

[0019] The attached diagram lists the components represented by each number as follows: 1. Crystallization sedimentation tank; 2. Softening and clarification tank; 3. Multi-media filter; 4. Electrocatalytic oxidation device; 5. Activated carbon filter; 6. Ultrafiltration device; 7. Primary nanofiltration device; 8. Secondary nanofiltration device; 9. High-salt reverse osmosis device; 10. MVR evaporation crystallization device; 11. Reclaimed water tank. Detailed Implementation

[0020] The principles and features of this utility model are described below with reference to the accompanying drawings. The examples given are only for explaining this utility model and are not intended to limit the scope of this utility model.

[0021] Example 1 like Figure 1As shown, a zero-discharge treatment system for para-aramid refining wastewater includes: a crystallization sedimentation tank 1, a softening and clarification tank 2, a multi-media filter 3, an electrocatalytic oxidation device 4, an activated carbon filter 5, an ultrafiltration device 6, a primary nanofiltration device 7, a secondary nanofiltration device 8, a high-salt reverse osmosis device 9, and an MVR evaporation and crystallization device 10. The crystallization sedimentation tank 1, softening and clarification tank 2, multi-media filter 3, electrocatalytic oxidation device 4, activated carbon filter 5, ultrafiltration device 6, primary nanofiltration device 7, secondary nanofiltration device 8, high-salt reverse osmosis device 9, and MVR evaporation and crystallization device 10 are connected in sequence. The concentrated water produced by the primary nanofiltration device 7 is returned to the crystallization sedimentation tank 1, and the concentrated water produced by the secondary nanofiltration device 8 is returned to the inlet of the ultrafiltration device 6. The crystallization sedimentation tank 1 is equipped with a calcium chloride solution dosing device, and the softening and clarification tank 2 is equipped with a sodium carbonate solution dosing device, a NaOH dosing device, a PFS (polyferric sulfate) dosing device, a PAM (polyacrylamide) dosing device, and a concentrated sulfuric acid dosing device.

[0022] The specific process is as follows: The refined wastewater generated during the production of protective para-aramid enters the crystallization sedimentation tank 1. At the same time, the crystallization sedimentation tank 1 can also receive the concentrated water generated by the first-stage nanofiltration device 7. The mixture is mixed and reacted by adding calcium chloride solution, and then crystallized at room temperature in the crystallization sedimentation tank 1 to produce dihydrate calcium sulfate sludge. The solid content of the sludge can reach 10% to remove most of the sulfate ions in the water. The wastewater treated by the crystallization sedimentation tank 1 enters the softening and clarification tank 2, where NaOH, NaCO3 and PFS are added for mixing and reaction. Then, PAM is added to the softening and clarification tank 2 to separate the sludge and water, remove most of the hardness in the water and prevent scaling of the subsequent membrane system. The solid content of the produced sludge is 5%, and the pH of the effluent is adjusted to about 7 by adding concentrated sulfuric acid. After being treated in softening and clarification tank 2, the wastewater enters multi-media filter 3, which effectively removes suspended solids and large crystalline particles from the water and prevents clogging of subsequent process equipment. The wastewater treated by the multi-media filter 3 enters the electrocatalytic oxidation device 4, which removes some organic pollutants from the water and plays an important role in preventing biofouling of the subsequent membrane system. The wastewater treated by the electrocatalytic oxidation device 4 enters the activated carbon filter 5 for further adsorption and removal of organic pollutants in the water, effectively preventing biofouling of the subsequent membrane system. The wastewater treated by the activated carbon filter 5 enters the ultrafiltration unit 6, which further removes fine suspended solids, organic particles, colloidal substances, bacteria, macromolecules, etc., to ensure the safe and stable operation of the subsequent membrane system. The wastewater treated by the ultrafiltration unit 6 enters the first-stage nanofiltration unit 7 for salt separation, intercepting most of the divalent ions. The sulfate ion removal rate reaches more than 99.5%, improving the purity of the sodium chloride solution in the product water. The wastewater treated by the first-stage nanofiltration unit 7 enters the second-stage nanofiltration unit 8 for further salt separation and interception of the remaining divalent ions. The sulfate ion removal rate reaches more than 97.5%, and the sodium chloride solution produced is of extremely high purity. The wastewater treated by the secondary nanofiltration unit 8 enters the high-salt reverse osmosis unit 9 to concentrate the high-purity sodium chloride solution, greatly increasing its salt content and reducing the amount of water in the sodium chloride solution. This reduces the scale of the subsequent evaporation and crystallization system and lowers investment. The high-salt reverse osmosis unit 9 has a recovery rate of 70% and a concentrated water salt content of 12.5%. The concentrated water treated by the high-salt reverse osmosis unit 9 enters the MVR evaporation and crystallization unit 10 to evaporate and crystallize the extremely high concentration of sodium chloride solution, producing qualified sodium chloride industrial salt products. Its quality can reach the industrial grade II dry salt standard and has economic value.

[0023] The refined wastewater generated during the production of para-aramid fibers for protective applications is characterized by high salt content, high hardness, and relatively high COD concentration, making it very difficult to treat. By rationally configuring a combination of pretreatment processes, sulfate ions, hardness, and COD can be effectively removed. Then, the wastewater is separated by membrane technology, and finally, high-quality sodium chloride industrial salt is recovered through evaporation and crystallization. The entire system, except for some sludge that is transported and disposed of externally, has no wastewater discharge, truly achieving the goal of zero discharge. At the same time, it recovers qualified reclaimed water and sodium chloride industrial salt. The system has a high degree of automation and operates safely and stably.

[0024] In response to the extremely high chloride ion content in the refining wastewater generated during the production of protective para-aramid fibers, the process pipeline materials are configured as follows to prevent chloride ions from corroding metal components: low-pressure pipelines use UPVC, high-pressure pipelines use 2205 stainless steel, and for pipelines with high wear resistance due to calcium sulfate crystallization sludge, these pipelines use more wear-resistant PE. Structures and carbon steel equipment in contact with wastewater are protected with 7 layers of oil and 5 layers of cloth using fiberglass for corrosion protection. Some metal equipment, accessories, or materials are made of 2205 stainless steel to ensure the service life of the project.

[0025] Example 2 like Figure 1 As shown, this embodiment is a further improvement on embodiment 1, as detailed below: The calcium chloride solution dosing device is used to add a 40% calcium chloride solution. The solids content of the sludge produced by the crystallization sedimentation tank 1 is 10%.

[0026] Example 3 like Figure 1As shown, this embodiment is a further improvement on embodiment 1 or 2, as detailed below: The sodium carbonate solution dosing device is used to add a 10% sodium carbonate solution, and the solids content of the sludge produced by softening and clarifying tank 2 is 5%.

[0027] Example 4 like Figure 1 As shown, this embodiment is a further improvement on any one of embodiments 1 to 3, as detailed below: The media filter 3 uses quartz sand and anthracite as fillers, with filling heights of 800mm and 400mm respectively. The quartz sand has a particle size of 0.5mm to 1.2mm and a non-uniformity coefficient K80 < 2.0. The anthracite has a particle size of 0.8mm to 1.8mm and a non-uniformity coefficient K80 < 1.7.

[0028] Example 5 like Figure 1 As shown, this embodiment is a further improvement on any one of embodiments 1 to 4, as detailed below: The electrocatalytic oxidation device 4 is equipped with a circulating reflux pump to ensure the treatment effect. The COD removal rate in water can reach 40%. The electrocatalytic oxidation device 4 is equipped with a waste gas treatment device to deal with the waste gas generated during the electrocatalytic oxidation process.

[0029] Example 6 like Figure 1 As shown, this embodiment is a further improvement on any one of embodiments 1 to 5, as detailed below: The filter media of activated carbon filter 5 are made of quartz sand and activated carbon, with filling heights of 200mm and 1500mm respectively. The particle size of the quartz sand is 1.0mm to 2.0mm, and the non-uniformity coefficient K80 < 2.0. The particle size of the activated carbon is 8 mesh to 16 mesh, and the non-uniformity coefficient K80 < 1.7.

[0030] Example 7 like Figure 1 As shown, this embodiment is a further improvement on any one of embodiments 1 to 6, as detailed below: For wastewater treatment, the membrane element selected for ultrafiltration device 6 is an external pressure ultrafiltration membrane. Ultrafiltration device 6 is equipped with a cross-flow operation pipeline. The recovery rate of ultrafiltration device 6 is 85%. A self-cleaning filter is installed in the front end of ultrafiltration device 6. The filtration accuracy of the self-cleaning filter is 50μm. Ultrafiltration device 6 is equipped with a backwashing system. While ensuring the safe and stable operation of ultrafiltration device 6 itself, it also ensures the safe and stable operation of the subsequent membrane system. The effluent quality of ultrafiltration device 6 can reach NTU less than 1.

[0031] Example 8 like Figure 1 As shown, this embodiment is a further improvement on any one of embodiments 1 to 7, as detailed below: The first-stage nanofiltration unit 7 adopts a two-stage structure and is equipped with an inter-stage booster pump to improve the recovery rate, which is 72%. The first-stage nanofiltration unit 7 is equipped with a security filter with a filtration accuracy of 5μm in the front section to effectively protect the safety of the nanofiltration membrane. The first-stage nanofiltration unit 7 is equipped with a non-oxidizing bactericide dosing device, a hydrochloric acid dosing device, a reducing agent dosing device, and a scale inhibitor dosing device. The dosing method of the non-oxidizing bactericide dosing device is shock dosing, which effectively avoids possible scaling and biological contamination. The concentrate from the first-stage nanofiltration unit 7 is returned to the crystallization sedimentation tank for treatment and no wastewater is discharged externally.

[0032] Example 9 like Figure 1 As shown, this embodiment is a further improvement on any one of embodiments 1 to 8, as detailed below: The secondary nanofiltration unit 8 adopts a three-stage structure with a recovery rate of 90%. The front section of the secondary nanofiltration unit 8 is equipped with a security filter with a filtration accuracy of 5μm. The secondary nanofiltration unit 8 is equipped with a non-oxidizing bactericide dosing device and a scale inhibitor dosing device. The dosing method of the non-oxidizing bactericide dosing device is shock dosing, which effectively avoids possible scaling and biological contamination. The concentrate from the secondary nanofiltration unit 8 is returned to the ultrafiltration unit 6 for treatment, and no wastewater is discharged externally.

[0033] Example 10 like Figure 1 As shown, this embodiment is a further improvement on any one of embodiments 1 to 9, as detailed below: The permeate from the high-salt reverse osmosis unit 9 enters the recycled water tank 11 and can be used for enterprise production; the condensate produced from the MVR evaporation crystallization unit 10 enters the recycled water tank 11 and can be used for enterprise production.

[0034] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A zero-discharge treatment system for wastewater from the refining of para-aramid fibers for protective purposes, characterized in that, include: The system comprises a crystallization sedimentation tank (1), a softening and clarification tank (2), a multi-media filter (3), an electrocatalytic oxidation device (4), an activated carbon filter (5), an ultrafiltration device (6), a primary nanofiltration device (7), a secondary nanofiltration device (8), a high-salt reverse osmosis device (9), and an MVR evaporation crystallization device (10). The device (8), the high-salt reverse osmosis device (9), and the MVR evaporation crystallization device (10) are connected in sequence. The concentrated water produced by the first-stage nanofiltration device (7) is returned to the crystallization sedimentation tank (1), and the concentrated water produced by the second-stage nanofiltration device (8) is returned to the inlet of the ultrafiltration device (6). The crystallization sedimentation tank (1) is equipped with a calcium chloride solution dosing device. The softening and clarification tank (2) is equipped with a sodium carbonate solution dosing device, a NaOH dosing device, a PFS dosing device, a PAM dosing device, and a concentrated sulfuric acid dosing device.

2. The zero-discharge treatment system for refining para-aramid fiber for protective purposes according to claim 1, characterized in that, The calcium chloride solution dosing device is used to add a calcium chloride solution with a concentration of 40%.

3. The zero-discharge treatment system for refining para-aramid fiber for protective purposes according to claim 1, characterized in that, The sodium carbonate solution dosing device is used to add a 10% sodium carbonate solution.

4. The zero-discharge treatment system for refining para-aramid fiber for protective purposes according to claim 1, characterized in that, The filler material of the multi-media filter (3) is made of quartz sand and anthracite, with filling heights of 800 mm and 400 mm respectively; the quartz sand has a particle size of 0.5 mm to 1.2 mm and a non-uniformity coefficient K80 < 2.0; the anthracite has a particle size of 0.8 mm to 1.8 mm and a non-uniformity coefficient K80 < 1.

7.

5. A zero-discharge treatment system for wastewater from the refining of para-aramid fibers for protective purposes, as described in claim 1, is characterized in that... The electrocatalytic oxidation device (4) is equipped with a circulating reflux pump and a waste gas treatment device.

6. The zero-discharge treatment system for refining para-aramid fiber for protective purposes according to claim 1, characterized in that, The activated carbon filter (5) uses quartz sand and activated carbon as fillers, with filling heights of 200 mm and 1500 mm respectively; the quartz sand has a particle size of 1.0 mm to 2.0 mm and a non-uniformity coefficient K80 < 2.0; the activated carbon has a particle size of 8 mesh to 16 mesh and a non-uniformity coefficient K80 < 1.

7.

7. A zero-discharge treatment system for refining para-aramid fiber for protective purposes according to claim 1, characterized in that, The membrane element selected by the ultrafiltration device (6) is an external pressure ultrafiltration membrane. The ultrafiltration device (6) is equipped with a cross-flow operation pipeline. The front end of the ultrafiltration device (6) is equipped with a self-cleaning filter. The ultrafiltration device (6) is equipped with a backwashing system.

8. A zero-discharge treatment system for wastewater from the refining of para-aramid fibers for protective purposes, as described in claim 1, is characterized in that... The first-stage nanofiltration device (7) adopts a two-stage structure and is equipped with an inter-stage booster pump; the first-stage nanofiltration device (7) is equipped with a security filter with a filtration accuracy of 5μm at the front end; the first-stage nanofiltration device (7) is equipped with a non-oxidizing bactericide dosing device, a hydrochloric acid dosing device, a reducing agent dosing device and a scale inhibitor dosing device; the dosing method of the non-oxidizing bactericide dosing device is shock dosing.

9. A zero-discharge treatment system for wastewater from the refining of para-aramid fibers for protective purposes, as described in claim 1, is characterized in that... The secondary nanofiltration device (8) adopts a three-section structure. The front section of the secondary nanofiltration device (8) is equipped with a security filter with a filtration accuracy of 5μm. The secondary nanofiltration device (8) is equipped with a non-oxidizing bactericide dosing device and a scale inhibitor dosing device. The dosing method of the non-oxidizing bactericide dosing device is shock dosing.

10. A zero-discharge treatment system for wastewater from the refining of para-aramid fibers for protective purposes, as described in claim 1, is characterized in that... The permeate from the high-salt reverse osmosis unit (9) enters the recycled water tank (11); the condensate produced in the MVR evaporation crystallization unit (10) enters the recycled water tank (11).

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