Membrane concentration system and wastewater zero discharge system with same

Abstract

The utility model provides a membrane concentration system and a wastewater zero discharge system with the same. The membrane concentration system comprises a first-stage membrane concentration module, a nanofiltration salt separation module, a second-stage membrane concentration module and a third-stage membrane concentration module which are sequentially arranged, carrying out primary membrane concentration treatment on the wastewater to be concentrated by using a primary membrane concentration module to obtain primary concentrated water; carrying out nanofiltration salt separation treatment on the first-stage concentrated water by using a nanofiltration salt separation module to obtain nanofiltration produced water; carrying out secondary membrane concentration treatment on the nanofiltration produced water by using a secondary membrane concentration module to obtain secondary concentrated water; and performing third-stage membrane concentration treatment on the second-stage concentrated water by using a third-stage membrane concentration module to obtain third-stage concentrated water. According to the membrane concentration system and the wastewater zero discharge system with the membrane concentration system, the salt content of the obtained third-stage concentrated water can be effectively improved, so that the water quantity conveyed to the evaporative crystallization module can be reduced, the investment cost of an evaporative crystallizer can be further reduced, the operation pressure of the system is lower, and the energy consumption can be saved.

Description

Technical Field

[0001] The utility model relates to the technical field of wastewater treatment, in particular to a membrane concentration system and a wastewater zero-discharge system having the same. Background Art

[0002] With the continuous development of industry, the discharge of improperly treated industrial wastewater into the environment has caused ecological pollution to the aquatic ecosystem. In the current situation of fresh water shortage, people's environmental awareness has gradually increased, and regulations on industrial wastewater management have become increasingly stringent. All industries are advocating for the resource utilization of wastewater to achieve minimal or zero liquid discharge of wastewater. Zero wastewater discharge refers to the treatment of industrial wastewater to achieve full (over 99%) recycling and reuse, and the salts and pollutants in the water are concentrated and crystallized and discharged in solid form or used as chemical raw materials.

[0003] In zero-discharge wastewater projects, the membrane elements used in traditional wastewater concentration systems require high desalination rates, resulting in low-salinity product water and high system operating pressures. This high operating pressure increases energy consumption and results in low total dissolved solids (TDS) concentrations in the concentrate side of the system, typically reaching only 80,000 mg / L, leading to large concentrate volumes. Consequently, larger evaporative crystallizers are required, increasing investment costs. Utility Model Content

[0004] The purpose of the present utility model is to provide a membrane concentration system and a wastewater zero discharge system having the same, so as to solve one or more problems existing in the prior art of the wastewater concentration system, such as high operating pressure, high energy consumption, low concentration of concentrated water and large amount of concentrated water after concentration, which leads to increased investment cost of evaporation crystallizer.

[0005] To achieve the above-mentioned purpose, the present invention is implemented through the following technical solutions: a membrane concentration system, comprising a first-stage membrane concentration module, a nanofiltration salt separation module, a second-stage membrane concentration module and a third-stage membrane concentration module arranged in sequence; the first-stage membrane concentration module is configured to perform a first-stage membrane concentration treatment on the wastewater to be concentrated to obtain a first-stage concentrated water; the nanofiltration salt separation module is configured to perform a nanofiltration salt separation treatment on the first-stage concentrated water to obtain nanofiltration product water; the second-stage membrane concentration module is configured to perform a second-stage membrane concentration treatment on the nanofiltration product water to obtain a second-stage concentrated water; the third-stage membrane concentration module is configured to perform a third-stage membrane concentration treatment on the second-stage concentrated water to obtain a third-stage concentrated water.

[0006] Optionally, the first-stage membrane concentration module includes a first-stage membrane concentration unit, which includes a first-stage membrane element with a desalination rate of not less than 97%; the second-stage membrane concentration module includes a second-stage membrane concentration unit, which includes a second-stage membrane element with a desalination rate of not less than 98%; the third-stage membrane concentration module includes a third-stage membrane concentration unit, which includes a third-stage membrane element with a desalination rate of not less than 75% and not more than 85%.

[0007] Optionally, the nanofiltration salt separation module includes a concentrate pretreatment unit and a low-pressure nanofiltration unit arranged in sequence; the concentrate pretreatment unit is configured to perform concentrate pretreatment on the first-stage concentrate; the low-pressure nanofiltration unit is configured to perform low-pressure nanofiltration on the effluent obtained after the concentrate pretreatment to obtain the nanofiltration product water and nanofiltration concentrate.

[0008] Optionally, the concentrated water pretreatment unit includes an advanced oxidation treatment device and a resin softening treatment device arranged in sequence.

[0009] Optionally, the nanofiltration salt separation module also includes a high-pressure nanofiltration unit connected to both the concentrated water pretreatment unit and the low-pressure nanofiltration unit. The high-pressure nanofiltration unit is configured to perform high-pressure nanofiltration treatment on the nanofiltration concentrated water to obtain high-pressure nanofiltration concentrated water and high-pressure nanofiltration product water, and transport the high-pressure nanofiltration product water to the concentrated water pretreatment unit.

[0010] Optionally, the membrane concentration system further includes a reuse module, which is configured to reuse the first-stage water produced by the first-stage membrane concentration module, the second-stage water produced by the second-stage membrane concentration module, and the third-stage water produced by the tertiary membrane concentration module.

[0011] Optionally, the reuse module includes a purification reverse osmosis unit and a reuse water tank, the purification reverse osmosis unit is connected to the third-stage membrane concentration module, the reuse water tank and the first-stage membrane concentration module, and the reuse water tank is connected to the first-stage membrane concentration module and the second-stage membrane concentration module; the purification reverse osmosis unit is used to perform purification reverse osmosis treatment on the third-stage produced water, and to transport the obtained purified reverse osmosis produced water to the reuse water tank and to transport the obtained purified reverse osmosis concentrated water to the first-stage membrane concentration module; the reuse water tank is used to receive the purified reverse osmosis produced water, the first-stage produced water and the second-stage produced water.

[0012] To achieve the above-mentioned objectives, the present invention also provides a wastewater zero discharge system, comprising a wastewater pretreatment module, an evaporation crystallization module and the membrane concentration system described in any one of the above items; the wastewater pretreatment module is configured to perform wastewater pretreatment on the wastewater to be treated to obtain the wastewater to be concentrated; the evaporation crystallization module comprises a first evaporation crystallization unit connected to the nanofiltration salt separation module and a second evaporation crystallization unit connected to the three-stage membrane concentration module; the first evaporation crystallization unit is configured to perform evaporation crystallization treatment on the high-pressure nanofiltration concentrated water of the nanofiltration salt separation module to obtain sodium sulfate salt; the second evaporation crystallization unit is configured to perform evaporation crystallization treatment on the third-stage concentrated water to obtain sodium chloride salt.

[0013] Optionally, the wastewater pretreatment module includes a coagulation and sedimentation unit and a filtration unit arranged in sequence; the coagulation and sedimentation unit is configured to perform coagulation and sedimentation treatment on the wastewater to be treated; the filtration unit is configured to perform filtration treatment on the effluent obtained after the coagulation and sedimentation treatment to obtain the wastewater to be concentrated.

[0014] Optionally, the filtration unit includes an ultrafiltration device.

[0015] Compared with the prior art, the membrane concentration system and the wastewater zero discharge system provided by the present invention have the following beneficial effects:

[0016] The membrane concentration system provided by the present invention comprises a first-stage membrane concentration module, a nanofiltration salt separation module, a second-stage membrane concentration module and a third-stage membrane concentration module which are arranged in sequence; the first-stage membrane concentration module is configured to perform a first-stage membrane concentration treatment on the wastewater to be concentrated to obtain first-stage concentrated water; the nanofiltration salt separation module is configured to perform a nanofiltration salt separation treatment on the first-stage concentrated water to obtain nanofiltration product water; the second-stage membrane concentration module is configured to perform a second-stage membrane concentration treatment on the nanofiltration product water to obtain second-stage concentrated water; the third-stage membrane concentration module is configured to perform a third-stage membrane concentration treatment on the second-stage concentrated water to obtain third-stage concentrated water. Thus, the membrane concentration system provided by the present invention performs a first-level membrane concentration treatment on the wastewater to be concentrated by a first-level membrane concentration module (including but not limited to a first-level membrane concentration unit), which can effectively remove pollutants in the wastewater to be concentrated, and can improve the salt content of the first-level concentrated water and improve the purity of the first-level product water; then, the first-level concentrated water is subjected to nanofiltration salt separation treatment by a nanofiltration salt separation module (including but not limited to a concentrated water pretreatment unit, a low-pressure nanofiltration unit and a high-pressure nanofiltration unit), which can effectively remove organic matter and hardness in the first-level concentrated water and can separate sodium sulfate and sodium chloride in the first-level concentrated water; then, the nanofiltration product water is subjected to a second-level membrane concentration treatment by a second-level membrane concentration module (including but not limited to a second-level membrane concentration unit), which can improve the salt content of the second-level concentrated water and improve the purity of the second-level product water. Further, the second-level concentrated water is subjected to a third-level membrane concentration treatment by a third-level membrane concentration module (including but not limited to a third-level membrane concentration unit), which can effectively improve the salt content of the third-level concentrated water, thereby reducing the amount of water transported to the evaporation crystallization module, and thus reducing the investment cost of the evaporation crystallizer. In addition, the membrane concentration system provided by the utility model has a low operating pressure and can save energy.

[0017] Furthermore, the membrane concentration system further includes a reuse module configured to reuse the first-stage water produced by the first-stage membrane concentration module, the second-stage water produced by the second-stage membrane concentration module, and the third-stage water produced by the third-stage membrane concentration module. Thus, the membrane concentration system provided by the present invention, by providing a reuse module (including but not limited to a purification reverse osmosis unit and a reuse water tank), can achieve resource utilization of wastewater and contribute to environmental protection.

[0018] The wastewater zero discharge system provided by the present invention comprises a wastewater pretreatment module, an evaporation crystallization module and the membrane concentration system described in any one of the above items; the wastewater pretreatment module is configured to perform wastewater pretreatment on the wastewater to be treated to obtain the wastewater to be concentrated; the evaporation crystallization module comprises a first evaporation crystallization unit connected to the nanofiltration salt separation module and a second evaporation crystallization unit connected to the three-stage membrane concentration module; the first evaporation crystallization unit is configured to perform evaporation crystallization treatment on the high-pressure nanofiltration concentrated water of the nanofiltration salt separation module to obtain sodium sulfate salt; the second evaporation crystallization unit is configured to perform evaporation crystallization treatment on the third-stage concentrated water to obtain sodium chloride salt. Thus, the wastewater zero discharge system provided by the present invention performs wastewater pretreatment on the wastewater to be treated by the wastewater pretreatment module (including but not limited to a coagulation sedimentation unit and a filtration unit), can remove impurities, particles, suspended matter, etc. in the wastewater to be treated, obtain wastewater to be concentrated, so as to meet the water inlet requirements of the membrane concentration system, thereby creating favorable conditions for the subsequent membrane concentration process. Concentrating the wastewater to be concentrated using a membrane concentration system can increase the concentration of the concentrated concentrate and reduce the amount of concentrate delivered to the evaporation and crystallization module, thereby reducing the investment cost of the evaporation and crystallization module. In addition, since the zero-discharge wastewater system provided by the present invention includes the membrane concentration system provided by the present invention, the zero-discharge wastewater system provided by the present invention has at least all the advantages of the membrane concentration system provided by the present invention. For the advantages of the zero-discharge wastewater system provided by the present invention, please refer to the relevant description of the beneficial effects of the membrane concentration system provided by the present invention, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a structural block diagram of a membrane concentration system provided in Example 1 of the present utility model;

[0020] Figure 2 A process flow chart of a membrane concentration system provided in Example 1 of the present utility model;

[0021] Figure 3 This is a structural block diagram of a zero wastewater discharge system provided in Example 2 of the present utility model;

[0022] Figure 4 A process flow chart of a zero wastewater discharge system provided in Example 2 of the present utility model;

[0023] Figure 5 This is a flow chart of a wastewater zero discharge method provided in Example 3 of the present utility model; the accompanying drawings are described as follows:

[0024] 1-first-stage membrane concentration module, 11-first-stage membrane concentration unit, 2-nanofiltration salt separation module, 21-concentrated water pretreatment unit, 211-advanced oxidation treatment device, 212-resin softening treatment device, 22-low-pressure nanofiltration unit, 23-high-pressure nanofiltration unit, 3-second-stage membrane concentration module, 31-second-stage membrane concentration unit, 4-third-stage membrane concentration module, 41-third-stage membrane concentration unit, 5-reuse module, 51-purification reverse osmosis unit, 52-reuse water tank, 6-wastewater pretreatment module, 61-coagulation and sedimentation unit, 62-filtration unit, 7-evaporation crystallization module, 71-first evaporation crystallization unit, 72-second evaporation crystallization unit. DETAILED DESCRIPTION

[0025] The following is a further detailed description of the membrane concentration system and the wastewater zero discharge system with the same proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer according to the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, please refer to the drawings. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions for the implementation of the present invention. Any structural modification, change in proportional relationship or adjustment of size, as long as the effect and purpose that can be achieved by the present invention are the same or similar, should still fall within the scope of the technical content disclosed by the present invention. The specific design features of the present invention disclosed herein, including, for example, specific dimensions, directions, positions and shapes, will be determined in part by the specific application and use environment. Furthermore, in the embodiments described below, the same reference numerals may be used in common among different drawings to indicate the same parts or parts having the same functions, and their repeated descriptions may be omitted.

[0026] Example 1

[0027] This embodiment provides a membrane concentration system. Figure 1 and Figure 2 , Figure 1 A structural block diagram of the membrane concentration system provided in this embodiment; Figure 2 The process flow chart of the membrane concentration system provided in this embodiment. Figure 1 and Figure 2It can be seen that the membrane concentration system includes a first-stage membrane concentration module 1, a nanofiltration salt separation module 2, a second-stage membrane concentration module 3 and a third-stage membrane concentration module 4 arranged in sequence; the first-stage membrane concentration module 1 is configured to perform a first-stage membrane concentration treatment on the wastewater to be concentrated to obtain a first-stage concentrated water; the nanofiltration salt separation module 2 is configured to perform a nanofiltration salt separation treatment on the first-stage concentrated water to obtain nanofiltration product water; the second-stage membrane concentration module 3 is configured to perform a second-stage membrane concentration treatment on the nanofiltration product water to obtain a second-stage concentrated water; the third-stage membrane concentration module 4 is configured to perform a third-stage membrane concentration treatment on the second-stage concentrated water to obtain a third-stage concentrated water. Therefore, the membrane concentration system provided in this embodiment performs a first-level membrane concentration treatment on the wastewater to be concentrated through a first-level membrane concentration module 1 (including but not limited to a first-level membrane concentration unit 11), which can effectively remove pollutants in the wastewater to be concentrated, and can improve the salt content of the first-level concentrated water obtained and improve the purity of the first-level product water obtained; then, the first-level concentrated water is subjected to nanofiltration salt separation treatment through a nanofiltration salt separation module 2 (including but not limited to a concentrated water pretreatment unit 21, a low-pressure nanofiltration unit 22 and a high-pressure nanofiltration unit 23), which can effectively remove organic matter and hardness in the first-level concentrated water, and can separate sodium sulfate and sodium chloride salts in the first-level concentrated water; and then the nanofiltration product water is subjected to a second-level membrane concentration treatment through a second-level membrane concentration module 3 (including but not limited to a second-level membrane concentration unit 31), which can improve the salt content of the second-level concentrated water obtained and improve the purity of the second-level product water obtained. Furthermore, the third-stage membrane concentration module 4 (including but not limited to the third-stage membrane concentration unit 41) performs a third-stage membrane concentration treatment on the second-stage concentrated water, effectively increasing the salinity of the resulting third-stage concentrated water. This reduces the amount of water delivered to the evaporation and crystallization module 7, thereby reducing the investment cost of the evaporation crystallizer. Furthermore, the membrane concentration system provided in this embodiment operates at a low pressure, not exceeding 70 bar, thereby saving energy.

[0028] Preferably, the primary membrane concentration module 1 includes a primary membrane concentration unit 11, which includes a first-stage membrane element with a salt rejection rate of no less than 97%; the secondary membrane concentration module 3 includes a secondary membrane concentration unit 31, which includes a second-stage membrane element with a salt rejection rate of no less than 98%; and the tertiary membrane concentration module 4 includes a tertiary membrane concentration unit 41, which includes a third-stage membrane element with a salt rejection rate of no less than 75% and no more than 85%. Thus, by using high-salinity first-stage membrane elements in the primary membrane concentration unit 11 and high-salinity second-stage membrane elements in the secondary membrane concentration unit 31, the first-stage and second-stage produced water can meet or exceed industrial water quality standards, allowing direct reuse in the production line. Furthermore, the salt content of the first-stage and second-stage concentrated water can be increased. Next, by using a third-stage membrane element with a low desalination rate in the third-stage membrane concentration unit 41, the amount of concentrate can be reduced and the salt content of the third-stage concentrate can be increased, so that the concentration of total dissolved solids (TDS) on the concentrate side of the system can be no less than 120,000 mg / L, thereby reducing the investment cost of the subsequent evaporation crystallizer.

[0029] Exemplarily, the first-stage membrane element includes a first-stage one-stage membrane and a first-stage two-stage membrane, and the first-stage membrane concentration unit 11 includes a first-stage booster pump, a first-stage safety filter, a first-stage high-pressure pump, the first-stage one-stage membrane, a first-stage inter-stage booster pump and the first-stage two-stage membrane arranged in sequence; the second-stage membrane element includes a second-stage one-stage membrane and a second-stage two-stage membrane, and the second-stage membrane concentration unit 31 includes a second-stage booster pump, a second-stage safety filter, a second-stage high-pressure pump, the second-stage one-stage membrane, a second-stage inter-stage booster pump and the second-stage two-stage membrane arranged in sequence; the third-stage membrane element is a special membrane, including a third-stage one-stage membrane and a third-stage two-stage membrane, and the third-stage membrane concentration unit 41 includes a third-stage booster pump, a third-stage safety filter, a third-stage high-pressure pump, the third-stage one-stage membrane and the third-stage two-stage membrane arranged in sequence. Since the third-stage membrane element is a special membrane, an inter-stage booster pump does not need to be provided between the third-stage first-stage membrane and the third-stage second-stage membrane in the three-stage membrane concentration unit 41, which can reduce the operating pressure of the membrane concentration system, save system energy consumption, and thus reduce the membrane concentration treatment cost.

[0030] It should be noted that this embodiment does not impose any specific restrictions on the specific values ​​of the salt rejection rates and membrane types of the first-stage membrane elements, the second-stage membrane elements, and the third-stage membrane elements. For example, in some exemplary embodiments, the first-stage membrane elements include anti-fouling brackish water membranes with a salt rejection rate of 99.5%, the second-stage membrane elements include anti-fouling brackish water membranes with a salt rejection rate of 99.7%, and the third-stage membrane elements include high-concentration-ratio specialty membrane elements with a salt rejection rate of 80%.

[0031] Preferably, the nanofiltration salt separation module 2 includes a concentrated water pretreatment unit 21 and a low-pressure nanofiltration unit 22 arranged in sequence; the concentrated water pretreatment unit 21 is configured to perform concentrated water pretreatment on the first-stage concentrated water; the low-pressure nanofiltration unit 22 is configured to perform low-pressure nanofiltration treatment on the effluent obtained after the concentrated water pretreatment to obtain the nanofiltration product water and nanofiltration concentrated water. Therefore, by first pretreating the first-stage concentrated water through the concentrated water pretreatment unit 21, organic matter and hardness in the first-stage concentrated water can be effectively removed, thereby ensuring the stable operation of the subsequent low-pressure nanofiltration unit 22 and extending the service life of the low-pressure nanofiltration unit 22. By performing low-pressure nanofiltration treatment on the effluent obtained after the concentrated water pretreatment by the low-pressure nanofiltration unit 22, sodium sulfate and sodium chloride in the first-stage concentrated water can be separated, laying a good foundation for the subsequent acquisition of sodium sulfate salt and sodium chloride salt.

[0032] For example, in some exemplary embodiments, the brine pretreatment unit 21 may be an advanced oxidation treatment device 211 and a resin softening treatment device 212 arranged in sequence. Thus, the advanced oxidation treatment device 211 can remove organic matter from the first-stage brine, and the resin softening treatment device 212 can remove hardness from the first-stage brine.

[0033] Furthermore, the nanofiltration salt separation module 2 also includes a high-pressure nanofiltration unit 23 connected to both the concentrated water pretreatment unit 21 and the low-pressure nanofiltration unit 22. The high-pressure nanofiltration unit 23 is configured to perform high-pressure nanofiltration treatment on the nanofiltration concentrated water to obtain high-pressure nanofiltration concentrated water and high-pressure nanofiltration product water, and to transport the high-pressure nanofiltration product water to the concentrated water pretreatment unit 21. Thus, the high-pressure nanofiltration concentrated water is obtained by the high-pressure nanofiltration unit 23 through the high-pressure nanofiltration treatment of the nanofiltration concentrated water, which lays a good foundation for the subsequent acquisition of sodium sulfate salt; by transporting the high-pressure nanofiltration product water obtained after the high-pressure nanofiltration treatment to the concentrated water pretreatment unit 21 for concentrated water pretreatment, the water quality can be improved and the wastewater discharge can be reduced, laying a good foundation for achieving zero wastewater discharge.

[0034] Preferably, the membrane concentration system further includes a recycling module 5, which is configured to reuse the first-stage water produced by the first-stage membrane concentration module 1, the second-stage water produced by the second-stage membrane concentration module 3, and the third-stage water produced by the tertiary membrane concentration module 4. Thus, by providing the recycling module 5 (including but not limited to the purification reverse osmosis unit 51 and the recycling water tank 52), wastewater can be recycled, which helps protect the environment.

[0035] For example, in some exemplary embodiments, the reuse module 5 includes a purification reverse osmosis unit 51 and a reuse water tank 52. The purification reverse osmosis unit 51 is connected to the tertiary membrane concentration module 4, the reuse water tank 52, and the primary membrane concentration module 1. The reuse water tank 52 is connected to the primary membrane concentration module 1 and the secondary membrane concentration module 3. The purification reverse osmosis unit 51 is used to purify the third-stage produced water by reverse osmosis treatment and transport the resulting purified reverse osmosis produced water to the reuse water tank 52, and to transport the resulting purified reverse osmosis concentrated water to the primary membrane concentration module 1. The reuse water tank 52 is used to receive the purified reverse osmosis produced water, the first-stage produced water, and the second-stage produced water. Thus, by purifying the third-stage produced water by reverse osmosis treatment by the purification reverse osmosis unit 51, purified reverse osmosis produced water that meets industrial water standards can be obtained, and by transporting the purified reverse osmosis produced water to the reuse water tank 52, water resources can be rationally utilized. By delivering the purified reverse osmosis concentrate to the primary membrane concentration module 1, wastewater discharge can be effectively reduced and water resource utilization can be improved. The purified reverse osmosis product water, the first-stage product water, and the second-stage product water are received by the recycling water tank 52 and can be directly reused in the production line, thereby improving economic benefits.

[0036] Example 2

[0037] This embodiment provides a wastewater zero discharge system. Figure 3 and Figure 4 , Figure 3 A structural block diagram of the zero wastewater discharge system provided in this embodiment; Figure 4 The process flow chart of the zero wastewater discharge system provided in this embodiment. Figure 3 and Figure 4 It can be seen that the wastewater zero discharge system includes a wastewater pretreatment module 6, an evaporation crystallization module 7 and the membrane concentration system described in any of the above embodiments; the wastewater pretreatment module 6 is configured to perform wastewater pretreatment on the wastewater to be treated to obtain the wastewater to be concentrated; the evaporation crystallization module 7 includes a first evaporation crystallization unit 71 connected to the nanofiltration salt separation module 2 and a second evaporation crystallization unit 72 connected to the three-stage membrane concentration module 4; the first evaporation crystallization unit 71 is configured to perform evaporation crystallization treatment on the high-pressure nanofiltration concentrated water of the nanofiltration salt separation module 2 to obtain sodium sulfate salt; the second evaporation crystallization unit 72 is configured to perform evaporation crystallization treatment on the third-stage concentrated water to obtain sodium chloride salt.

[0038] Therefore, the wastewater zero discharge system provided in this embodiment performs wastewater pretreatment on the wastewater to be treated through the wastewater pretreatment module 6 (including but not limited to the coagulation sedimentation unit 61 and the filtration unit 62), which can remove impurities, particles, suspended matter, etc. in the wastewater to be treated, and obtain wastewater to be concentrated, so as to meet the water inlet requirements of the membrane concentration system, thereby creating favorable conditions for the subsequent membrane concentration process. By concentrating the wastewater to be concentrated through the membrane concentration system, the concentration of the concentrated concentrated water can be increased and the amount of concentrated water transported to the evaporation crystallization module 7 can be reduced, thereby reducing the investment cost of the evaporation crystallization module 7. In addition, since the wastewater zero discharge system provided in this embodiment includes the membrane concentration system provided in any of the above-mentioned embodiments, the wastewater zero discharge system provided in this embodiment has at least all the advantages of the membrane concentration system provided in the above-mentioned embodiments. For the advantages of the wastewater zero discharge system provided in this embodiment, please refer to the relevant description of the beneficial effects of the membrane concentration system provided in the above-mentioned embodiments, which will not be repeated here.

[0039] It should be noted that, as those skilled in the art can understand, the present invention does not impose too many restrictions on the type of the wastewater to be treated. The wastewater to be treated can be, but is not limited to, coking wastewater.

[0040] Preferably, the wastewater pretreatment module 6 includes a coagulation and sedimentation unit 61 and a filtration unit 62, which are arranged in sequence; the coagulation and sedimentation unit 61 is configured to perform coagulation and sedimentation treatment on the wastewater to be treated; and the filtration unit 62 is configured to filter the effluent obtained after the coagulation and sedimentation treatment to obtain the wastewater to be concentrated. Thus, the coagulation and sedimentation treatment of the wastewater to be treated by the coagulation and sedimentation unit 61 allows the calcium and magnesium ions and suspended matter in the wastewater to be treated to form flocs and settle; and the filtration treatment of the effluent obtained after the coagulation and sedimentation treatment by the filtration unit 62 can reduce the sludge density index of the wastewater, thereby meeting the water inlet requirements of the subsequent membrane concentration system.

[0041] For example, in some exemplary embodiments, the coagulation and sedimentation unit 61 may include a coagulation and sedimentation tank (not shown) and a reagent dosing device (not shown). When the wastewater to be treated is transported to the coagulation and sedimentation tank, a chemical softener and a coagulant are added to the coagulation and sedimentation tank via the reagent dosing device. The filtration unit 62 may be an ultrafiltration device (not shown), which performs ultrafiltration on the effluent obtained after the coagulation and sedimentation treatment, thereby achieving higher filtration accuracy.

[0042] Example 3

[0043] This embodiment provides a method for zero wastewater discharge, which is used in the zero wastewater discharge system described in any of the above embodiments. Figure 5 , Figure 5 The following is a flow chart of the zero wastewater discharge method provided in this embodiment. Figure 5 It can be seen that the zero wastewater discharge method includes:

[0044] S100: transporting the wastewater to be treated to the wastewater pretreatment module 6 for wastewater pretreatment to obtain wastewater to be concentrated;

[0045] S200: transporting the wastewater to be concentrated to the primary membrane concentration module 1 for primary membrane concentration treatment to obtain first-stage concentrated water;

[0046] S300: The first-stage concentrated water is transported to the nanofiltration salt separation module 2 for nanofiltration salt separation treatment to obtain nanofiltration product water;

[0047] S400: The nanofiltration product water is transported to the secondary membrane concentration module 3 for secondary membrane concentration treatment to obtain second-stage concentrated water;

[0048] S500: transporting the secondary concentrated water to the tertiary membrane concentration module 4 for tertiary membrane concentration treatment to obtain third-level concentrated water;

[0049] S600: transporting the first-stage produced water of the first-stage membrane concentration module 1, the second-stage produced water of the second-stage membrane concentration module 3, and the third-stage produced water of the third-stage membrane concentration module 4 to the reuse module 5 for reuse treatment;

[0050] S700: transporting the high-pressure nanofiltration concentrated water from the nanofiltration salt separation module 2 to the first evaporation crystallization unit 71 for evaporation crystallization to obtain sodium sulfate salt;

[0051] S800: The third-stage concentrated water is transported to the second evaporation crystallization unit 72 for evaporation crystallization treatment to obtain sodium chloride salt.

[0052] Therefore, the zero wastewater discharge method provided in this embodiment and the zero wastewater discharge system provided in any of the above-mentioned embodiments belong to the same inventive concept. Therefore, the zero wastewater discharge method provided in this embodiment has at least all the advantages of the zero wastewater discharge systems provided in the above-mentioned embodiments, and the zero wastewater discharge systems provided in the above-mentioned embodiments and the membrane concentration systems provided in the above-mentioned embodiments belong to the same inventive concept. Therefore, for the advantages of the zero wastewater discharge method provided in this embodiment, please refer to the relevant description of the beneficial effects of the membrane concentration systems provided in the above-mentioned embodiments, and no further details will be given here.

[0053] It should be noted that, as those skilled in the art can understand, this embodiment does not impose too many restrictions on the order of the above-mentioned steps S700 and S800. In some embodiments, step S700 can be performed first, and then step S800; in other embodiments, step S800 can be performed first, and then step S700; in other embodiments, step S700 and step S800 can also be performed at the same time.

[0054] In summary, the membrane concentration system provided by the present invention and the wastewater zero discharge system having the same have the following advantages: the membrane concentration system provided by the present invention includes a first-stage membrane concentration module, a nanofiltration salt separation module, a second-stage membrane concentration module and a third-stage membrane concentration module arranged in sequence; the first-stage membrane concentration module is configured to perform a first-stage membrane concentration treatment on the wastewater to be concentrated to obtain a first-stage concentrated water; the nanofiltration salt separation module is configured to perform a nanofiltration salt separation treatment on the first-stage concentrated water to obtain nanofiltration product water; the second-stage membrane concentration module is configured to perform a second-stage membrane concentration treatment on the nanofiltration product water to obtain a second-stage concentrated water; the third-stage membrane concentration module is configured to perform a third-stage membrane concentration treatment on the second-stage concentrated water to obtain a third-stage concentrated water. Thus, the membrane concentration system provided by the present invention performs a first-level membrane concentration treatment on the wastewater to be concentrated by a first-level membrane concentration module (including but not limited to a first-level membrane concentration unit), which can effectively remove pollutants in the wastewater to be concentrated, and can improve the salt content of the first-level concentrated water and improve the purity of the first-level product water; then, the first-level concentrated water is subjected to nanofiltration salt separation treatment by a nanofiltration salt separation module (including but not limited to a concentrated water pretreatment unit, a low-pressure nanofiltration unit and a high-pressure nanofiltration unit), which can effectively remove organic matter and hardness in the first-level concentrated water and can separate sodium sulfate and sodium chloride in the first-level concentrated water; then, the nanofiltration product water is subjected to a second-level membrane concentration treatment by a second-level membrane concentration module (including but not limited to a second-level membrane concentration unit), which can improve the salt content of the second-level concentrated water and improve the purity of the second-level product water. Further, the second-level concentrated water is subjected to a third-level membrane concentration treatment by a third-level membrane concentration module (including but not limited to a third-level membrane concentration unit), which can effectively improve the salt content of the third-level concentrated water, thereby reducing the amount of water transported to the evaporation crystallization module, and thus reducing the investment cost of the evaporation crystallizer. In addition, the membrane concentration system provided by the utility model has a low operating pressure and can save energy.

[0055] Furthermore, the membrane concentration system further includes a reuse module configured to reuse the first-stage water produced by the first-stage membrane concentration module, the second-stage water produced by the second-stage membrane concentration module, and the third-stage water produced by the third-stage membrane concentration module. Thus, the membrane concentration system provided by the present invention, by providing a reuse module (including but not limited to a purification reverse osmosis unit and a reuse water tank), can achieve resource utilization of wastewater and contribute to environmental protection.

[0056] The wastewater zero discharge system provided by the present invention comprises a wastewater pretreatment module, an evaporation crystallization module and the membrane concentration system described in any one of the above items; the wastewater pretreatment module is configured to perform wastewater pretreatment on the wastewater to be treated to obtain the wastewater to be concentrated; the evaporation crystallization module comprises a first evaporation crystallization unit connected to the nanofiltration salt separation module and a second evaporation crystallization unit connected to the three-stage membrane concentration module; the first evaporation crystallization unit is configured to perform evaporation crystallization treatment on the high-pressure nanofiltration concentrated water of the nanofiltration salt separation module to obtain sodium sulfate salt; the second evaporation crystallization unit is configured to perform evaporation crystallization treatment on the third-stage concentrated water to obtain sodium chloride salt. Thus, the wastewater zero discharge system provided by the present invention performs wastewater pretreatment on the wastewater to be treated by the wastewater pretreatment module (including but not limited to a coagulation sedimentation unit and a filtration unit), can remove impurities, particles, suspended matter, etc. in the wastewater to be treated, obtain wastewater to be concentrated, so as to meet the water inlet requirements of the membrane concentration system, thereby creating favorable conditions for the subsequent membrane concentration process. Concentrating the wastewater to be concentrated using a membrane concentration system can increase the concentration of the concentrated concentrate and reduce the amount of concentrate delivered to the evaporation and crystallization module, thereby reducing the investment cost of the evaporation and crystallization module. In addition, since the zero-discharge wastewater system provided by the present invention includes the membrane concentration system provided by the present invention, the zero-discharge wastewater system provided by the present invention has at least all the advantages of the membrane concentration system provided by the present invention. For the advantages of the zero-discharge wastewater system provided by the present invention, please refer to the relevant description of the beneficial effects of the membrane concentration system provided by the present invention, which will not be repeated here.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A membrane concentration system, characterized in that: It includes a primary membrane concentration module, a nanofiltration salt separation module, a secondary membrane concentration module and a tertiary membrane concentration module which are arranged in sequence; The first-stage membrane concentration module is configured to perform a first-stage membrane concentration treatment on the wastewater to be concentrated to obtain first-stage concentrated water; The nanofiltration salt separation module is configured to perform nanofiltration salt separation on the first-stage concentrated water to obtain nanofiltration product water; The secondary membrane concentration module is configured to perform secondary membrane concentration treatment on the nanofiltration produced water to obtain second-stage concentrated water; The three-stage membrane concentration module is configured to perform three-stage membrane concentration treatment on the second-stage concentrated water to obtain third-stage concentrated water.

2. The membrane concentration system according to claim 1, wherein The first-stage membrane concentration module includes a first-stage membrane concentration unit, which includes a first-stage membrane element with a desalination rate of not less than 97%; the second-stage membrane concentration module includes a second-stage membrane concentration unit, which includes a second-stage membrane element with a desalination rate of not less than 98%; the third-stage membrane concentration module includes a third-stage membrane concentration unit, which includes a third-stage membrane element with a desalination rate of not less than 75% and not more than 85%.

3. The membrane concentration system according to claim 1, wherein The nanofiltration salt separation module includes a concentrate pretreatment unit and a low-pressure nanofiltration unit arranged in sequence; the concentrate pretreatment unit is configured to perform concentrate pretreatment on the first-stage concentrate; the low-pressure nanofiltration unit is configured to perform low-pressure nanofiltration on the effluent obtained after the concentrate pretreatment to obtain the nanofiltration product water and nanofiltration concentrate.

4. The membrane concentration system according to claim 3, wherein: The concentrated water pretreatment unit includes an advanced oxidation treatment device and a resin softening treatment device which are arranged in sequence.

5. The membrane concentration system according to claim 3, wherein: The nanofiltration salt separation module also includes a high-pressure nanofiltration unit connected to both the concentrated water pretreatment unit and the low-pressure nanofiltration unit. The high-pressure nanofiltration unit is configured to perform high-pressure nanofiltration treatment on the nanofiltration concentrated water to obtain high-pressure nanofiltration concentrated water and high-pressure nanofiltration product water, and transport the high-pressure nanofiltration product water to the concentrated water pretreatment unit.

6. The membrane concentration system according to claim 1, wherein: The membrane concentration system further includes a reuse module, which is configured to reuse the first-stage water produced by the first-stage membrane concentration module, the second-stage water produced by the second-stage membrane concentration module, and the third-stage water produced by the tertiary membrane concentration module.

7. The membrane concentration system according to claim 6, wherein: The reuse module includes a purification reverse osmosis unit and a reuse water tank. The purification reverse osmosis unit is connected to the three-stage membrane concentration module, the reuse water tank and the first-stage membrane concentration module, and the reuse water tank is connected to the first-stage membrane concentration module and the second-stage membrane concentration module. The purification reverse osmosis unit is used to purify the third-stage produced water by reverse osmosis treatment, and transport the obtained purified reverse osmosis produced water to the reuse water tank and the obtained purified reverse osmosis concentrated water to the first-stage membrane concentration module. The reuse water tank is used to receive the purified reverse osmosis produced water, the first-stage produced water and the second-stage produced water.

8. A zero wastewater discharge system, characterized in that: It comprises a wastewater pretreatment module, an evaporation crystallization module and a membrane concentration system as described in any one of claims 1 to 7; the wastewater pretreatment module is configured to perform wastewater pretreatment on the wastewater to be treated to obtain the wastewater to be concentrated; the evaporation crystallization module comprises a first evaporation crystallization unit connected to the nanofiltration salt separation module and a second evaporation crystallization unit connected to the three-stage membrane concentration module; the first evaporation crystallization unit is configured to perform evaporation crystallization treatment on the high-pressure nanofiltration concentrated water of the nanofiltration salt separation module to obtain sodium sulfate salt; the second evaporation crystallization unit is configured to perform evaporation crystallization treatment on the third-stage concentrated water to obtain sodium chloride salt.

9. The zero wastewater discharge system according to claim 8, characterized in that: The wastewater pretreatment module includes a coagulation and sedimentation unit and a filtration unit arranged in sequence; the coagulation and sedimentation unit is configured to perform coagulation and sedimentation treatment on the wastewater to be treated; the filtration unit is configured to perform filtration treatment on the effluent obtained after the coagulation and sedimentation treatment to obtain the wastewater to be concentrated.

10. The zero wastewater discharge system according to claim 9, characterized in that: The filtration unit includes an ultrafiltration device.

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