System for treating clean sewage

Abstract

The utility model discloses a system for treating clean sewage. The system comprises a flocculent precipitation device, a medium filtering device, an ultrafiltration device and a reverse osmosis device which are sequentially communicated through a pipeline, wherein the reverse osmosis device comprises a first-section reverse osmosis unit, a second-section reverse osmosis unit and a third-section reverse osmosis unit, the water inlet end of the first-section reverse osmosis unit is communicated with the water outlet end of the ultrafiltration device through a pipeline, and the concentrated water outlet end of the first-section reverse osmosis unit is communicated with the water inlet end of the second-section reverse osmosis unit through a pipeline; the concentrated water outlet end of the second-section reverse osmosis unit is communicated with the water inlet end of the third-section reverse osmosis unit through a pipeline, and the fresh water outlet end of the first-section reverse osmosis unit and / or the fresh water outlet end of the second-section reverse osmosis unit are / is communicated with a fresh water collecting tank through a pipeline; the fresh water outlet end of the third-section reverse osmosis unit is communicated with the water inlet end of the first-section reverse osmosis unit through a pipeline and / or the fresh water outlet end of the third-section reverse osmosis unit is communicated with a fresh water collecting tank through a pipeline.

Description

Technical Field

[0001] This application relates to the field of environmental engineering, and more specifically, to a system for treating clean wastewater. Background Technology

[0002] Manufacturing enterprises commonly use circulating water systems to cool production equipment. During the operation of these systems, the salt concentration of the circulating water gradually increases due to evaporation, and the introduction of impurities such as dust also increases the turbidity. To maintain water quality, the circulating water system needs to periodically discharge some of the high-concentration wastewater and replenish it with fresh water. However, directly discharging this wastewater would result in a waste of precious water resources.

[0003] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art. Utility Model Content

[0004] In a first aspect, this application provides a system for treating purified wastewater, comprising a flocculation sedimentation device, a media filtration device, an ultrafiltration device, and a reverse osmosis device sequentially connected by pipelines; the flocculation sedimentation device is used to remove suspended particles and colloidal particles from the purified wastewater; the media filtration device is used to remove suspended solids from the purified wastewater; the ultrafiltration device is used to remove microparticles, colloids, microbial debris, and high molecular weight substances from the purified wastewater; the reverse osmosis device is used to remove salt from the purified wastewater; the reverse osmosis device includes a first reverse osmosis unit, a second reverse osmosis unit, and a third reverse osmosis unit, wherein the first... The inlet of one reverse osmosis unit is connected to the outlet of the ultrafiltration device via a pipeline. The concentrate outlet of the first reverse osmosis unit is connected to the inlet of the second reverse osmosis unit via a pipeline. The concentrate outlet of the second reverse osmosis unit is connected to the inlet of the third reverse osmosis unit via a pipeline. The desalination outlet of the first and / or the desalination outlet of the second reverse osmosis unit is connected to a desalination collection tank via a pipeline. The desalination outlet of the third reverse osmosis unit is connected to the inlet of the first reverse osmosis unit via a pipeline and / or the desalination outlet of the third reverse osmosis unit is connected to the desalination collection tank via a pipeline. Therefore, through the treatment system of this application, the desalination recovery rate can reach 90%, the desalination conductivity is reduced to 200μs / cm-350μs / cm, and the desalination can be directly reused for industrial production. The concentrate, after decalcification treatment, re-enters the reuse tank and is pumped to the reuse water supply network for industrial production. The treatment system described in this application achieves efficient treatment of clean sewage.

[0005] In some embodiments, the first reverse osmosis unit, the second reverse osmosis unit, and the third reverse osmosis unit each include at least one reverse osmosis pressure vessel, and a reverse osmosis membrane is disposed inside the reverse osmosis pressure vessel. Thus, the reverse osmosis membrane can remove salt from the purified wastewater.

[0006] In some embodiments, the ratio of the number of reverse osmosis membranes in the first reverse osmosis unit to the number of reverse osmosis membranes in the second reverse osmosis unit is (1.6-2.6):1. Therefore, by adjusting the ratio of the number of reverse osmosis membranes in the first and second reverse osmosis units, the distribution of water flux can be optimized, which helps to improve the overall water production capacity and desalination efficiency of the treatment system.

[0007] In some embodiments, the ratio of the number of reverse osmosis membranes in the second reverse osmosis unit to that in the third reverse osmosis unit is (1-1.4):1. Thus, the second reverse osmosis unit further removes salt from the purified wastewater based on the first reverse osmosis unit, while the third reverse osmosis unit further treats the concentrate produced by the second reverse osmosis unit. By adjusting the ratio of the number of reverse osmosis membranes in the second and third reverse osmosis units, the desalination efficiency can be improved while simultaneously increasing the freshwater recovery rate of the system, reducing water waste.

[0008] In some embodiments, the desalination rate of the reverse osmosis membrane in the third reverse osmosis unit is lower than that of the reverse osmosis membranes in the first and second reverse osmosis units. Therefore, using a reverse osmosis membrane with a lower desalination rate in the third reverse osmosis unit can reduce the reverse osmosis operating pressure, lower energy consumption, and simultaneously improve water production efficiency.

[0009] In some embodiments, the reverse osmosis membrane includes a refurbished membrane, which is an aromatic polyamide membrane. Therefore, the use of a refurbished membrane can reduce the operating pressure of reverse osmosis, achieving cost savings; simultaneously, the use of a refurbished membrane can improve the freshwater recovery rate, and the quality of the freshwater produced by the wastewater treatment system is close to that of the production water, allowing it to be directly reused as production water, thus alleviating the problem of excessively high-quality freshwater caused by over-treatment and resulting in resource waste.

[0010] In some embodiments, the system further includes regulating valves, which include a first regulating valve and a second regulating valve. The first regulating valve is located on the pipeline between the freshwater outlet of the third reverse osmosis unit and the inlet of the first reverse osmosis unit. The second regulating valve is located on the pipeline between the freshwater outlet of the third reverse osmosis unit and the freshwater collection tank. Therefore, by controlling the opening and closing of the first and second regulating valves, the destination of the secondary freshwater can be flexibly adjusted, maintaining the quality of the treated water.

[0011] In some embodiments, a secondary booster pump is further included, which is installed on the pipeline at the inlet end of the reverse osmosis unit. Thus, the secondary booster pump supplies pressure to the reverse osmosis unit, allowing purified wastewater to pass through the reverse osmosis membrane while retaining salts, enabling the reverse osmosis process to proceed effectively.

[0012] In some embodiments, the operating pressure of the secondary booster pump is 0.3-0.67 MPa.

[0013] In some embodiments, a security filter is further included, which is installed on the inlet pipe of the reverse osmosis unit. This security filter further filters out any quartz sand or anthracite particles that may be carried in the treated wastewater, preventing impurities from entering the reverse osmosis unit.

[0014] In some embodiments, the flocculation sedimentation device has a sludge discharge port at the sedimentation point of suspended particles and colloidal particles, and the sludge discharge port is connected to a filter press via a pipeline. Thus, the flocculent material settled at the bottom of the flocculation sedimentation tank is promptly discharged to the filter press through the sludge discharge port, preventing the flocculent material from re-suspending.

[0015] In some embodiments, the media filtration device comprises layers of quartz sand and anthracite arranged perpendicular to the liquid flow direction. Thus, the combination of the quartz sand and anthracite layers provides filter media with different pore sizes, effectively adsorbing and purifying suspended solids of varying particle sizes from the wastewater.

[0016] In some embodiments, the thickness ratio of the quartz sand layer to the anthracite coal seam is (4-5):1.

[0017] In some embodiments, the particle size of the quartz sand in the quartz sand layer is 0.5 mm to 15 mm.

[0018] In some embodiments, the anthracite coal in the anthracite seam has a particle size of 1 mm to 2 mm.

[0019] In some embodiments, the ultrafiltration device is provided with an ultrafiltration membrane, the ultrafiltration membrane having a filtration accuracy of 0.02 μm.

[0020] In some embodiments, the purified wastewater satisfies at least one of the following conditions: the conductivity of the purified wastewater is 800 μs / cm-1500 μs / cm; and / or the temperature of the purified wastewater is 22°C-34°C; and / or the pH of the purified wastewater is 6-9; and / or the turbidity of the purified wastewater is less than or equal to 50 NTU. Attached Figure Description

[0021] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0022] Figure 1 This is a schematic diagram of a clean wastewater treatment system according to an embodiment of this application.

[0023] Explanation of reference numerals in the attached figures:

[0024] 1. Raw water tank; 2. Flocculation and sedimentation device; 21. Raw water supply pump; 22. Flocculation and sedimentation tank; 23. Sludge pump; 24. Filter press; 3. Media filtration device; 31. Media filter supply pump; 32. Media filter; 4. Ultrafiltration device; 41. Ultrafiltration supply pump; 42. Self-cleaning filter; 43. Ultrafiltration unit; 44. Ultrafiltration water tank; 5. Reverse osmosis device; 51. Reverse osmosis supply pump; 52. Security filter; 53. Secondary booster pump; 54. First stage reverse osmosis unit; 541. First freshwater outlet pipe; 55. Second stage reverse osmosis unit; 551. Second freshwater outlet pipe; 56. Third stage reverse osmosis unit; 561. Secondary freshwater outlet pipe; 57. First regulating valve; 58. Second regulating valve; 6. Freshwater collection tank; 61. Conductivity meter; 7. Concentrate collection tank. Detailed Implementation

[0025] The embodiments of this application 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 are only used to explain this application, and should not be construed as limiting this application.

[0026] In industrial production, circulating water systems are used for equipment cooling. The wastewater discharged from these systems, free of heavy metals and other harmful pollutants, is often referred to as clean wastewater. However, due to its high conductivity, clean wastewater is not suitable for direct reuse in production processes. Furthermore, using this relatively clean wastewater for simple operations with low water quality requirements, such as slag flushing, not only violates the principle of "cascade utilization" of water resources but also fails to fully utilize its potential value. Therefore, exploring and developing effective ways to utilize clean wastewater is crucial.

[0027] This application proposes a system for treating clean wastewater, wherein the clean wastewater to be treated meets at least one of the following conditions:

[0028] The electrical conductivity of clean sewage is 800 μs / cm-1500 μs / cm; and / or,

[0029] The temperature of the clean drain water is 22℃-34℃; and / or,

[0030] The pH of clean wastewater is 6-9; and / or,

[0031] The turbidity of clean wastewater is less than or equal to 50 NTU.

[0032] In some embodiments, the conductivity of the purified wastewater is 800 μs / cm to 1500 μs / cm. The conductivity of the purified wastewater includes, but is not limited to, 800 μs / cm, 900 μs / cm, 1000 μs / cm, 1100 μs / cm, 1200 μs / cm, 1300 μs / cm, 1400 μs / cm, or 1500 μs / cm.

[0033] In some embodiments, the temperature of the purified wastewater is 22°C-34°C. The temperature of the purified wastewater includes, but is not limited to, 22°C, 24°C, 26°C, 28°C, 30°C, 32°C, or 34°C.

[0034] In some embodiments, the pH of the purified wastewater is 6-9. The pH of the purified wastewater includes, but is not limited to, 6, 7, 8, or 9.

[0035] In some embodiments, the turbidity of the cleaned wastewater is less than or equal to 50 NTU. The turbidity of the cleaned wastewater includes, but is not limited to, 1 NTU, 2 NTU, 4 NTU, 6 NTU, 8 NTU, 10 NTU, 20 NTU, 30 NTU, 40 NTU, or 50 NTU.

[0036] To address the aforementioned clean water usage, this application provides a system for treating clean wastewater, specifically, see reference [link to relevant documentation]. Figure 1 The system comprises a flocculation sedimentation device 2, a media filtration device 3, an ultrafiltration device 4, and a reverse osmosis device 5, connected sequentially by pipelines. Thus, the treated wastewater first passes through the flocculation sedimentation device 2 to remove suspended particles and colloidal particles; then, it passes through the media filtration device 3 to further remove suspended solids; next, it passes through the ultrafiltration device 4 to further remove tiny particles, colloids, microbial debris, and high molecular weight substances; finally, it passes through the reverse osmosis device 5 to remove salts. The desalinated portion of the treated wastewater becomes freshwater, while the remaining portion becomes concentrated wastewater. Through this treatment system, the freshwater recovery rate can reach 90%, and the freshwater conductivity is reduced to 200 μs / cm-350 μs / cm. The freshwater can be directly reused for industrial production. The concentrated wastewater, after decalcification treatment, re-enters the reuse water tank and is then pumped to the reuse water supply network for industrial use, thereby achieving highly efficient treatment of the treated wastewater.

[0037] In some embodiments, the treatment system further includes a raw water tank 1 for collecting clean wastewater.

[0038] In some embodiments, the flocculation sedimentation device 2 includes a flocculation sedimentation tank 22. For example... Figure 1 As shown, the inlet of the flocculation sedimentation tank 22 is connected to the outlet of the raw water tank 1 through a pipeline.

[0039] Flocculants and bactericides are added to the flocculation sedimentation tank 22. The flocculant can be polyferric sulfate or polyacrylamide, and the bactericide can be sodium hypochlorite. The flocculant destabilizes suspended particles and colloidal particles in the treated wastewater, causing them to aggregate and form large flocs. These flocs then settle to the bottom of the flocculation sedimentation tank 22. The bactericide removes bacteria from the treated wastewater, improving the hygiene and safety of the water quality.

[0040] In some embodiments, the flocculation sedimentation device 2 further includes a raw water supply pump 21, a sludge discharge pump 23, and a filter press 24. For example... Figure 1 As shown, the raw water supply pump 21 is installed on the pipeline between the raw water tank 1 and the flocculation sedimentation tank 22. The raw water supply pump 21 ensures a continuous and stable flow of clean wastewater from the raw water tank 1 to the flocculation sedimentation tank 22. The bottom of the flocculation sedimentation tank 22 is equipped with two sludge discharge ports, which are connected to the filter press 24 via pipelines. A sludge discharge pump 23 is installed on the pipeline between the sludge discharge ports and the filter press 24. Under the action of the sludge discharge pump 23, the flocculent material settled at the bottom of the flocculation sedimentation tank 22 is promptly discharged through the sludge discharge ports to the filter press 24, preventing the flocculent material from re-suspending. The filter press 24 filters the discharged sludge, reducing the water content in the sludge and facilitating subsequent sludge treatment and disposal.

[0041] In some embodiments, the media filtering device 3 includes a media filter 32, such as Figure 1 As shown, the inlet of the media filter 32 is connected to the outlet of the flocculation sedimentation tank 22 via a pipeline. The outlet of the flocculation sedimentation tank 22 is located on the side wall of the flocculation sedimentation tank 22, which facilitates the flow of the supernatant from the flocculation sedimentation tank 22 into the media filter 32.

[0042] In some embodiments, the media filter 3 is provided with a layer of quartz sand and a layer of anthracite arranged perpendicular to the liquid flow direction. The inlet end of the media filter 32 is located at the top of the media filter 32. The supernatant flowing out of the flocculation sedimentation tank 22 passes sequentially through the quartz sand layer and the anthracite layer. The quartz sand layer first adsorbs the larger suspended solids, and then the anthracite layer adsorbs the smaller suspended solids. The combination of the quartz sand layer and the anthracite layer provides filter media with different pore sizes, which can effectively adsorb suspended solids of different particle sizes to fully remove suspended solids from the clean wastewater.

[0043] In some embodiments, the thickness ratio of the quartz sand layer to the anthracite seam is (4-5):1. The thickness ratio of the quartz sand layer to the anthracite seam includes, but is not limited to, 4:1, 4.2:1, 4.4:1, 4.6:1, 4.8:1 or 5:1.

[0044] In some embodiments, the particle size of the quartz sand in the quartz sand layer is 0.5mm-15mm. The particle size of the quartz sand in the quartz sand layer includes, but is not limited to, 0.5mm, 1mm, 2mm, 4mm, 6mm, 9mm, 12mm or 15mm.

[0045] In some embodiments, the particle size of anthracite in the anthracite seam is 1mm-2mm. The particle size of anthracite in the anthracite seam includes, but is not limited to, 0.5mm, 1mm, 2mm, 4mm, 6mm, 9mm, 12mm or 15mm.

[0046] In some embodiments, the media filtration device 3 further includes a media filter 32 and a water pump 31, such as Figure 1 As shown, the water supply pump 31 for the media filter 32 is installed on the pipeline between the flocculation sedimentation tank 22 and the media filter 32. The water supply pump 31 for the media filter 32 ensures that the supernatant in the flocculation sedimentation tank 22 flows continuously and stably into the media filter 32.

[0047] In some embodiments, the ultrafiltration device 4 includes an ultrafiltration unit 43. For example... Figure 1 As shown, the inlet of the ultrafiltration unit 43 and the outlet of the media filter 32 are connected by a pipeline.

[0048] In some embodiments, the ultrafiltration unit 43 includes at least one ultrafiltration container, with multiple ultrafiltration containers connected in parallel. The number of ultrafiltration containers that need to be connected in parallel to the ultrafiltration unit 43 can be determined based on the workload of the ultrafiltration process. Specifically, as shown... Figure 1 As shown, the ultrafiltration unit 43 includes three ultrafiltration containers connected in parallel.

[0049] In some embodiments, an ultrafiltration membrane is disposed within the ultrafiltration container. Thus, the permeate flowing from the media filter 32 passes through the ultrafiltration membrane, which removes fine particles, colloids, microbial debris, and macromolecules from the purified wastewater.

[0050] In some embodiments, the ultrafiltration membrane comprises a polyethersulfone (PES) membrane. Therefore, the PES membrane exhibits good chemical stability and mechanical strength, making it suitable for various water quality conditions; simultaneously, the PES membrane demonstrates high tolerance and durability, extending the service life of the ultrafiltration membrane.

[0051] In some embodiments, the filtration precision of the ultrafiltration membrane is not less than 0.02 μm; for example, the filtration precision of the ultrafiltration membrane can be 0.02 μm. Therefore, the high-precision ultrafiltration membrane can intercept most bacteria, viruses, colloids, large organic molecules, and other particulate matter larger than 0.02 μm, improving the water quality of the ultrafiltration permeate. Simultaneously, the high-precision ultrafiltration membrane helps reduce fouling of the reverse osmosis membrane, extending the maintenance cycle and service life of the purified wastewater system.

[0052] In some embodiments, the ultrafiltration device 4 further includes an ultrafiltration feed water pump 41, a self-cleaning filter 42, and an ultrafiltration water tank 44. For example... Figure 1 As shown, the ultrafiltration feed water pump 41 is installed on the pipeline between the media filter 32 and the ultrafiltration unit 43, ensuring a continuous and stable flow of clean water from the media filter 32 to the ultrafiltration unit 43. A self-cleaning filter 42 is installed on the pipeline between the ultrafiltration feed water pump 41 and the ultrafiltration unit 43. When a large amount of dirt adheres to the surface of the ultrafiltration membrane, the self-cleaning filter 42 can clean the surface of the ultrafiltration membrane, extending its service life and improving the efficiency of the treatment system. An ultrafiltration water tank 44 is installed on the pipeline between the ultrafiltration unit 43 and the reverse osmosis device 5. Clean water, after being filtered by the ultrafiltration device 4, is collected in the ultrafiltration water tank 44.

[0053] In some embodiments, the reverse osmosis device 5 includes an inlet end, a concentrate outlet end, and a desalination outlet end. The permeate flowing out of the ultrafiltration device 4 enters the reverse osmosis device 5 through the inlet end, and after its salt content is removed, it is discharged through the desalination outlet end for reuse, and concentrate is discharged through the concentrate outlet end.

[0054] Specifically, such as Figure 1 As shown, the reverse osmosis device 5 includes a first reverse osmosis unit 54, a second reverse osmosis unit 55, and a third reverse osmosis unit 56. The inlet of the first reverse osmosis unit 54 is connected to the outlet of the ultrafiltration tank 44 via a pipeline. The concentrate outlet of the first reverse osmosis unit 54 is connected to the inlet of the second reverse osmosis unit 55 via a pipeline. The concentrate outlet of the second reverse osmosis unit 55 is connected to the inlet of the third reverse osmosis unit 56 via a pipeline. The concentrate outlet of the third reverse osmosis unit 56 is connected to the concentrate collection tank 7.

[0055] The first reverse osmosis unit 54 has a first freshwater outlet pipe 541 connected to its freshwater outlet end, and the other end of the first freshwater outlet pipe 541 is connected to the freshwater collection tank 6. The second reverse osmosis unit 55 has a second freshwater outlet pipe 551 connected to its freshwater outlet end, and the other end of the second freshwater pipe is connected to the first freshwater outlet pipe 541. The freshwater obtained from the second reverse osmosis unit 55 is collected through the second freshwater outlet pipe 551 and flows into the first freshwater outlet pipe 541, where it flows into the freshwater collection tank 6 together with the freshwater obtained from the first reverse osmosis unit 54.

[0056] The freshwater outlet of the third reverse osmosis unit 56 is connected to a secondary freshwater outlet pipe 561, and the other end of the secondary freshwater outlet pipe 561 is connected to a pipeline between the ultrafiltration water tank 44 and the reverse osmosis feed water pump 51.

[0057] A branch pipe is installed between the first freshwater outlet pipe 541 and the secondary freshwater outlet pipe 561, and a second regulating valve 58 is installed on the branch pipe. Taking the position where the branch pipe connects to the secondary freshwater outlet pipe 561 as the starting point and the position where the pipeline between the ultrafiltration water tank 44 and the reverse osmosis feed water pump 51 connects to the secondary freshwater outlet pipe 561 as the ending point, a first regulating valve 57 is installed on the secondary freshwater outlet pipe 561.

[0058] Thus, the purified wastewater is desalinated by the reverse osmosis unit 5. The total freshwater recovery rate of the first reverse osmosis unit 54 and the second reverse osmosis unit 55 is not less than 80%, and the total desalination rate is 90%-95%. The third reverse osmosis unit 56 further treats the concentrated water produced by the second reverse osmosis unit 55. The secondary freshwater produced by the third reverse osmosis unit 56 has a recovery rate of not less than 50% and a desalination rate of 60%-80%.

[0059] In some embodiments, a conductivity meter 61 is further included at the freshwater collection tank 6. The conductivity meter 61 is used to monitor the conductivity of the freshwater tank. Conductivity is an important indicator for evaluating freshwater quality. If the conductivity of the freshwater in the collection tank 6 is too high, it indicates that the reverse osmosis membrane of the third-stage reverse osmosis unit 56 may have a reduced ability to remove salt, and the conductivity of the secondary freshwater increases. In this case, the second regulating valve 58 is closed, and the first regulating valve 57 is opened, allowing the secondary freshwater to return to the reverse osmosis unit 5 for secondary treatment. Therefore, by setting the first regulating valve 57 and the second regulating valve 58, the destination of the secondary freshwater can be flexibly adjusted to maintain the quality of the treated water.

[0060] In some embodiments, a distributed control system (DCS) is further provided to automatically control the first regulating valve 57 and the second regulating valve 58, so as to achieve precise regulation of the secondary freshwater destination. The treatment system can operate stably for a long time, while reducing manual intervention and improving the convenience and safety of operation.

[0061] In some embodiments, the first reverse osmosis unit 54, the second reverse osmosis unit 55, and the third reverse osmosis unit 56 each include at least one reverse osmosis pressure vessel. The multiple reverse osmosis pressure vessels of the first reverse osmosis unit 54 are connected in parallel, the multiple reverse osmosis pressure vessels of the second reverse osmosis unit 55 are connected in parallel, and the multiple reverse osmosis pressure vessels of the third reverse osmosis unit 56 are connected in parallel. The number of reverse osmosis pressure vessels that need to be connected in parallel in each reverse osmosis unit can be determined according to the workload of reverse osmosis processing.

[0062] In some embodiments, a reverse osmosis membrane is disposed within the reverse osmosis pressure vessel. Specifically, the number of reverse osmosis membranes is the same in all four reverse osmosis pressure vessels of the first reverse osmosis unit 54, the same in all two reverse osmosis pressure vessels of the second reverse osmosis unit 55, and the same in all two reverse osmosis pressure vessels of the third reverse osmosis unit 56. Thus, the reverse osmosis membrane is a semi-permeable membrane with extremely small pore sizes. Water in the purified wastewater permeates through the reverse osmosis membrane, while salt is retained. Therefore, the reverse osmosis membrane is used to remove salt from the purified wastewater.

[0063] In some embodiments, the ratio of the number of reverse osmosis membranes in the first reverse osmosis unit 54 to the number of reverse osmosis membranes in the second reverse osmosis unit 55 is (1.6-2.6):1. This ratio includes, but is not limited to, 1.6:1, 1.8:1, 2.0:1, 2.2:1, 2.4:1, or 2.6:1. Therefore, by adjusting the ratio of the number of reverse osmosis membranes in the first reverse osmosis unit 54 to the number of reverse osmosis membranes in the second reverse osmosis unit 55, the distribution of water flux can be optimized, which helps to improve the overall water production capacity and desalination efficiency of the treatment system. Simultaneously, a reasonable allocation of the number of reverse osmosis membranes can reduce the fouling rate of the reverse osmosis membranes and extend their service life.

[0064] In some embodiments, the ratio of the number of reverse osmosis membranes in the second reverse osmosis unit 55 to the third reverse osmosis unit 56 is (1-1.4):1. This ratio includes, but is not limited to, 1:1, 1.1:1, 1.2:1, 1.3:1, or 1.4:1. The second reverse osmosis unit 55 further removes salt from the purified wastewater based on the first reverse osmosis unit 54, while the third reverse osmosis unit 56 further treats the concentrate produced by the second reverse osmosis unit 55. By adjusting the ratio of the number of reverse osmosis membranes in the second and third reverse osmosis units 56, the desalination efficiency can be improved while simultaneously increasing the freshwater recovery rate of the system, thus reducing water waste.

[0065] In some embodiments, the reverse osmosis membrane includes a refurbished membrane, which includes an aromatic polyamide membrane. Since the desalination rate of a refurbished membrane is lower than that of a new membrane, its use can reduce the operating pressure of the reverse osmosis process, thus saving costs. Simultaneously, the use of a refurbished membrane can improve the freshwater recovery rate, ensuring that the quality of the freshwater produced by the wastewater treatment system is close to that of the production water, allowing for direct reuse as production water and avoiding the problem of excessively treating the freshwater and wasting resources. Aromatic polyamide membranes, due to their good chemical stability and durability, are suitable for reverse osmosis processes and can withstand high operating pressures and chemical cleaning.

[0066] In addition, the purified wastewater has a certain temperature, and temperature changes cause fluctuations in the conductivity of the purified wastewater. However, these temperature and conductivity changes are within the acceptable range for the operation of the reverse osmosis membrane. Therefore, there is no need to install heat exchange equipment at the inlet of the reverse osmosis unit 5 to regulate the water temperature due to seasonal changes, which reduces the complexity of the system and operating costs.

[0067] In some embodiments, a scale inhibitor and a reducing agent are also added to the reverse osmosis membrane. For example, the reducing agent may include NaHSO3. The scale inhibitor may include a reverse osmosis scale inhibitor, which includes, but is not limited to, phosphate scale inhibitors, polyelectrolyte scale inhibitors, or polycarboxylic acid scale inhibitors.

[0068] In some embodiments, the desalination rate of the reverse osmosis membrane in the third reverse osmosis unit 56 is lower than that of the reverse osmosis membranes in the first reverse osmosis unit 54 and the second reverse osmosis unit 55. The use of a newer membrane with a lower desalination rate in the third reverse osmosis unit 56 can reduce the reverse osmosis operating pressure, lower energy consumption, and simultaneously improve water production efficiency.

[0069] In some embodiments, the reverse osmosis unit 5 further includes a reverse osmosis feed water pump 51, a security filter 52, and a secondary booster pump 53. For example... Figure 1 As shown, the reverse osmosis feed water pump 51 is installed in the pipeline between the ultrafiltration water tank 44 and the reverse osmosis unit 5. The reverse osmosis feed water pump 51 ensures a continuous and stable flow of clean wastewater from the ultrafiltration water tank 44 to the reverse osmosis unit 5. A security filter 52 is installed in the pipeline between the reverse osmosis feed water pump 51 and the reverse osmosis unit 5. This further filters any quartz sand or anthracite particles that may be carried in the clean wastewater before reverse osmosis treatment, preventing impurities from entering the reverse osmosis unit 5. Before entering the reverse osmosis unit 5, the sludge density index (SDI) of the clean wastewater is less than 5.

[0070] The secondary booster pump 53 is installed on the pipeline between the security filter 52 and the reverse osmosis device 5. The secondary booster pump 53 is a variable frequency pump, which delivers pressure to the reverse osmosis device 5. Under the action of pressure, the water in the clean water passes through the reverse osmosis membrane, while the salt is retained, so that the reverse osmosis process can proceed effectively.

[0071] In some embodiments, the operating pressure of the secondary booster pump 53 is 0.3 MPa-0.67 MPa. The operating pressure of the secondary booster pump 53 includes, but is not limited to, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, or 0.67 MPa. Because the desalination rate of the reverse osmosis membrane in the third-stage reverse osmosis unit 56 is low, the water permeation resistance required for the concentrate produced by the second-stage reverse osmosis unit 55 to enter the third-stage reverse osmosis unit 56 is correspondingly reduced. Therefore, the water pressure after permeation in the second-stage reverse osmosis unit 55 is sufficient to drive the water flow into the third-stage reverse osmosis unit 56, thus eliminating the need for an additional booster pump to provide pressure to the third-stage reverse osmosis unit 56. Currently, in actual operation, the inventors have observed that the operating pressure of the secondary booster pump 53 is less than 0.67 MPa, and the minimum operating pressure can reach 0.3 MPa, indicating that the system can operate effectively even at lower pressures.

[0072] In some embodiments, manufacturing industrial enterprises include, but are not limited to, copper smelting enterprises and iron smelting enterprises.

[0073] Taking a copper smelting enterprise as an example, the wastewater discharged from the circulating water of its smelting, electrolysis, oxygen production, and acid production processes is approximately 2000 m³. 3 The conductivity of the wastewater discharged per day is 1046 μS / cm. Wastewater from each process is collected in raw water tank 1 and pumped to flocculation sedimentation tank 22 via raw water pump 21. Polyferric sulfate flocculant is added to flocculation sedimentation tank 22. The flocculant causes suspended particles and colloidal particles in the wastewater to aggregate into large flocs. After the flocs settle, the underflow containing the flocs is filtered by filter press 24, and the filtrate is returned to flocculation sedimentation tank 22. The supernatant in flocculation sedimentation tank 22 enters media filter 32. Media filter 32 is filled with a 220 mm thick layer of anthracite at the top and a 1000 mm thick layer of quartz sand at the bottom. After filtration by media filter 32, the supernatant re-enters ultrafiltration unit 43. After filtration by ultrafiltration unit 43, the ultrafiltration permeate is collected in ultrafiltration water tank 44. The permeate from the ultrafiltration tank 44, driven by the reverse osmosis feed pump 51, passes sequentially through the security filter 52 and then through the secondary booster pump 53 to the reverse osmosis unit 5. In the reverse osmosis unit 5, the first reverse osmosis unit 54 is equipped with 12 membrane housings, the second reverse osmosis unit 55 with 5 membrane housings, and the third reverse osmosis unit 56 with 5 membrane housings. The first and second membrane housings contain 6 membrane elements with approximately 90% desalination rate, and the third membrane housing contains 6 membrane elements with approximately 65% ​​desalination rate. In actual operation, the feed water flow rate of the reverse osmosis unit 5 is 90 m³ / s. 3 The operating pressure of the secondary booster pump 53 is 0.67 MPa, and the freshwater production is 73.6 m³ / h. 3 / h, secondary freshwater production is 8.3m³.3 / h, concentrate production 8.1m 3 / h, the conductivity of fresh water is 213μs / cm.

[0074] In the description of this application, "first feature" and "second feature" may include one or more of the features.

[0075] In the description of this application, "multiple" means two or more.

[0076] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0077] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A system for treating clean sewage, characterized in that, it comprises a flocculation and sedimentation device, a media filtration device, an ultrafiltration device, and a reverse osmosis device connected in sequence through pipelines; the flocculation and sedimentation device is used for removing suspended particles and colloidal particles in the clean sewage; the media filtration device is used for removing suspended solids in the clean sewage; the ultrafiltration device is used for removing micro-particles, colloids, microbial debris, and high molecular substances in the clean sewage; the reverse osmosis device is used for removing salt from the clean sewage; wherein the reverse osmosis device comprises a first-stage reverse osmosis unit, a second-stage reverse osmosis unit, and a third-stage reverse osmosis unit, the water inlet end of the first-stage reverse osmosis unit is connected to the water outlet end of the ultrafiltration device through a pipeline, the concentrated water outlet end of the first-stage reverse osmosis unit is connected to the water inlet end of the second-stage reverse osmosis unit through a pipeline, the concentrated water outlet end of the second-stage reverse osmosis unit is connected to the water inlet end of the third-stage reverse osmosis unit through a pipeline, the fresh water outlet end of the first-stage reverse osmosis unit and / or the fresh water outlet end of the second-stage reverse osmosis unit is connected to a fresh water collection tank through a pipeline, and the fresh water outlet end of the third-stage reverse osmosis unit is connected to the water inlet end of the first-stage reverse osmosis unit through a pipeline and / or connected to the fresh water collection tank through a pipeline.

2. The system of claim 1, wherein, The first-stage reverse osmosis unit, the second-stage reverse osmosis unit, and the third-stage reverse osmosis unit each comprises at least one reverse osmosis pressure vessel, and a reverse osmosis membrane is arranged in the reverse osmosis pressure vessel; Optionally, the number ratio of the reverse osmosis membranes of the first-stage reverse osmosis unit to the second-stage reverse osmosis unit is (1.6-2.6):1; Optionally, the number ratio of the reverse osmosis membranes of the second-stage reverse osmosis unit to the third-stage reverse osmosis unit is (1-1.4):1; Optionally, the desalination rate of the reverse osmosis membranes of the third-stage reverse osmosis unit is lower than that of the reverse osmosis membranes of the first-stage reverse osmosis unit and the second-stage reverse osmosis unit; Optionally, the reverse osmosis membranes comprise a new membrane, and the new membrane comprises an aromatic polyamide membrane.

3. The system of claim 1, wherein, Further comprising a regulating valve, the regulating valve comprises a first regulating valve and a second regulating valve; the first regulating valve is arranged on the pipeline between the fresh water outlet end of the third-stage reverse osmosis unit and the water inlet end of the first-stage reverse osmosis unit; and the second regulating valve is arranged on the pipeline between the fresh water outlet end of the third-stage reverse osmosis unit and the fresh water collection tank.

4. The system of claim 1, wherein, Further comprising a secondary booster pump, the secondary booster pump is arranged on the pipeline at the water inlet end of the reverse osmosis device.

5. The system of claim 4, wherein, The operating pressure of the secondary booster pump is 0.3-0.67 MPa.

6. The system of claim 1, wherein, Further comprising a security filter, the security filter is arranged on the pipeline at the water inlet end of the reverse osmosis device.

7. The system according to any of claims 1-6, characterized in that, A sludge discharge port is arranged at the position where the suspended particles and colloidal particles are precipitated in the flocculation and sedimentation device, and the sludge discharge port is connected to a filter press through a pipeline.

8. The system according to any of claims 1-6, characterized in that, A quartz sand layer and an anthracite layer are arranged in the media filtration device in a stacked manner perpendicular to the liquid flow direction. Optionally, the thickness ratio of the quartz sand layer to the anthracite layer is (4-5):

1. Optionally, the particle size of the quartz sand in the quartz sand layer is 0.5mm-15mm. Optionally, the particle size of the anthracite in the anthracite layer is 1mm-2mm.

9. The system according to any of claims 1-6, characterized in that, The ultrafiltration device is internally provided with an ultrafiltration membrane, and the filtration precision of the ultrafiltration membrane is 0.02μm.

10. The system of any of claims 1-6, wherein, The clean water meets at least one of the following conditions: The conductivity of the clean water is 800μs / cm-1500μs / cm; and / or, The temperature of the clean water is 22℃-34℃; and / or, The pH of the clean water is 6-9; and / or, The turbidity of the clean water is less than or equal to 50NTU.

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