CFRO-based countercurrent reverse osmosis membrane concentration method

Abstract

The invention discloses a CFRO (circulating fluid reverse osmosis)-based countercurrent reverse osmosis membrane concentration method, which comprises the steps of pretreatment, nanofiltration salt separation, seawater type reverse osmosis concentration, heat exchange, water quantity regulation, countercurrent reverse osmosis high-power concentration, pressure energy recovery and final waste liquid discharge. According to the method, a CFRO (reverse flow reverse osmosis) technology is taken as a core, a system structure and operating parameters are optimized, and a heat energy recovery device and a pressure energy recovery device are combined, so that a high-efficiency and high-recovery-rate membrane concentration process is realized. Under the condition that the operating pressure does not exceed 83 bar, the high-salinity wastewater can be concentrated to 260,000 mg / L TDS, the unit water production energy consumption is remarkably reduced and is 30% or above lower than that of traditional DTRO and UHPRO systems, and the system has good pollution resistance and operating stability and is suitable for high-salinity wastewater concentration and near-zero emission ZLD scenes in the industries of coal chemical industry, salt chemical industry, lithium batteries and the like.

Description

A CFRO-based countercurrent reverse osmosis membrane concentration method Technical Field

[0001] This invention relates to the field of high-salinity wastewater treatment technology, specifically to a countercurrent reverse osmosis membrane concentration method based on CFRO. Background Technology

[0002] With industrial development, especially in industries such as coal chemical, salt chemical, lithium battery, pharmaceutical, printing and dyeing, and electroplating, the discharge of high-salinity wastewater is constantly increasing. This wastewater generally contains high concentrations of inorganic salts, with TDS typically exceeding 50,000 mg / L, and some also contain recalcitrant organic matter. Direct discharge of this type of wastewater will cause serious pollution to the ecological environment. Therefore, wastewater treatment models with "near-zero discharge" or "minimal liquid discharge" are gradually becoming the direction of industry development.

[0003] Currently used high-salinity wastewater treatment processes, such as multi-effect evaporation (MED), mechanical vapor recompression (MVR), and ultra-high pressure reverse osmosis (UHPRO), each have certain limitations: evaporation methods have extremely high energy consumption, large equipment investment, and complex systems, making them unsuitable for small- to medium-sized industrial settings or those with high energy efficiency requirements; UHPRO systems operate at pressures as high as 90–120 bar, which not only leads to high costs for membrane modules and supporting equipment but also makes them prone to membrane fouling and structural fatigue, resulting in short service life and high maintenance costs; conventional reverse osmosis systems have limited concentration ratios, making it difficult to exceed 70,000-80,000 mg / L TDS, thus failing to meet the need for further reduction of high-concentration wastewater. Summary of the Invention

[0004] The purpose of this invention is to address the problems of high energy consumption, severe membrane fouling, complex system structure, and difficulty in achieving high concentration ratios in existing high-salinity wastewater concentration processes. It provides a CFRO-based countercurrent reverse osmosis membrane concentration method, combined with a specially designed high-pressure-resistant membrane module, breaking through the technical bottlenecks of conventional RO and UHPRO technologies in the field of high-concentration wastewater treatment. This system not only significantly reduces energy consumption but also possesses excellent fouling resistance and operational stability, making it suitable for various high-salinity wastewater concentration and near-zero discharge scenarios.The specific technical solution is as follows: A countercurrent reverse osmosis membrane concentration method based on CFRO includes the following steps: Step 1: Pretreatment; The raw wastewater S1 first enters the pretreatment system, where suspended solids, colloidal impurities, and some organic pollutants are removed through coagulation, sedimentation, and filtration to obtain pretreated effluent S2; Step 2: Nanofiltration desalination; The pretreated effluent S2 enters the nanofiltration desalination system, where divalent ions are retained to obtain nanofiltration concentrate S3 and nanofiltration permeate S4. The nanofiltration concentrate S3 is used as feed water, concentrate discharge, or for further treatment in subsequent seawater reverse osmosis (SWRO) systems; Step 3: Seawater reverse osmosis concentration; The nanofiltration concentrate S3 enters the seawater reverse osmosis (SWRO) system, where it is concentrated to the concentration endpoint through high-pressure reverse osmosis treatment to obtain SWRO concentrate S5 and SWRO permeate S6. The SWRO concentrate S5, as a high-salt, high-pressure fluid, enters the next stage of thermal energy... Optimization; Step 4: Heat Exchange; SWRO concentrate S5 and CFRO high-temperature concentrate S10 from the countercurrent reverse osmosis membrane concentration system exchange heat in the heat exchange system, recovering the heat from CFRO concentrate S8 to preheat SWRO concentrate S7; Step 5: Water Flow Adjustment; After heat exchange, SWRO concentrate S7 and CFRO concentrate S8 are mixed together and enter the water flow adjustment tank to achieve buffering, pressure stabilization, mixing, and temperature adjustment, obtaining the effluent S9 from the tank; Step 6: Countercurrent Reverse Osmosis High-Concentration; The effluent S9 from the tank enters... The countercurrent reverse osmosis (CFRO) membrane concentration system undergoes further high-concentration membrane operation to obtain CFRO permeate S11 and CFRO concentrate S12. CFRO permeate S11 is recycled for internal system cleaning or partially discharged. CFRO concentrate S12 is separated into a high-temperature concentrate stream S10 by the temperature control system and enters the heat exchanger. The remaining unutilized and high-pressure concentrate S13, after reaching the concentration endpoint, enters the pressure energy recovery stage. Step 7: Pressure Energy Recovery; The high-pressure concentrate S13 enters the pressure energy recovery device to recover high-pressure concentrate. The remaining pressure in the concentrate S13 can be transferred to the CFRO feed pump or used for other pressurized units within the system, and finally discharged as waste liquid S14. The CFRO countercurrent reverse osmosis membrane concentration system adopts a countercurrent operation mode of concentrate and feed water, combined with a cross-flow design, and uses external permeate aid to regulate the osmotic pressure gradient on both sides of the membrane. The CFRO countercurrent reverse osmosis membrane concentration system adopts a segmented series multi-effect countercurrent structure, with each segment independently adjusting the inlet and outlet flow rates and osmotic pressure matching state. The CFRO countercurrent reverse osmosis membrane concentration system is designed for high salt tolerance membrane systems with TDS >100,000 mg / L.

[0005] The nanofiltration desalination system separates monovalent and divalent ions, with the nanofiltration membrane in the system retaining divalent Ca ions in the water. 2+ Mg 2+ SO4 2- Na+ monovalent ion + Cl -Penetrates nanofiltration membrane.

[0006] Among them, the nanofiltration membrane is an aromatic polyamide composite nanofiltration membrane or a sulfonated polyethersulfone nanofiltration membrane.

[0007] The coagulant added during the coagulation process of the pretreatment system is one or more of polyaluminum chloride, polyferric sulfate, or polyacrylamide.

[0008] In this system, flow meters and thermometers are installed in all permeate and concentrate flow paths of the seawater reverse osmosis (SWRO) system and the countercurrent reverse osmosis (CFRO) membrane concentration system. Data is collected and analyzed through a control platform, and the temperature control system and flow regulation device are adjusted in a coordinated manner.

[0009] The operating pressure of the seawater reverse osmosis (SWRO) system is 50-70 bar, while the operating pressure of the countercurrent reverse osmosis (CFRO) system does not exceed 83 bar.

[0010] The heat exchange system uses shell-and-tube heat exchangers or plate heat exchangers, and the pressure energy recovery device is a pressure exchanger, a hydraulic turbine, or an energy recovery pump.

[0011] Among them, the overall recovery rate of high-salinity wastewater treated by the countercurrent reverse osmosis membrane concentration method reaches 50%-99.6%, and the energy consumption per unit of produced water is as low as 5.0 kWh / m³. 3 .

[0012] Compared with the closest existing technology, the technical solution provided by this invention has the following beneficial effects: 1. This invention significantly reduces energy consumption; The CFRO system enhances membrane shear force and mass transfer efficiency through countercurrent crossflow design, regulates osmotic pressure difference using external permeate aid, significantly reduces the required operating pressure, and integrates a pressure energy recovery device to efficiently recover residual pressure energy of concentrate, which can reduce the high-pressure pump load by more than 30%, and the unit permeate energy consumption can be as low as 5.0-5.8 kWh / m³. 3 Compared to traditional UHPRO systems, it saves up to 44% in costs.

[0013] 2. This invention can achieve ultra-high concentration ratios; the unique countercurrent operation and osmosis aid principle effectively overcome the limitations of high osmotic pressure. It adopts a segmented series multi-effect countercurrent structure to achieve efficient concentration at each stage. The system design breaks through the limitations of traditional RO and can directly treat high-salt wastewater or concentrated water with TDS > 100,000 mg / L. The overall recovery rate in Example 1 reaches 50%, and the system recovery rate in Example 2 is as high as 99.6%, which is the key to achieving minimum liquid discharge in MLD or zero liquid discharge in ZLD.

[0014] 3. This invention can effectively alleviate membrane fouling and extend membrane life; the strong membrane shear force generated by the countercurrent crossflow design significantly slows down the deposition of pollutants on the membrane surface; the nanofiltration pre-salt separation removes divalent ions that are prone to fouling in advance, greatly reducing the fouling pressure of subsequent RO / CFRO membranes; it reduces operating pressure and fouling risk, and together they significantly extend the service life of membrane modules.

[0015] 4. This invention can improve system stability and adaptability; the segmented series structure allows each segment to independently adjust the flow rate and osmotic pressure matching, making the system highly adaptable and easy to expand according to water quality and demand; the water volume adjustment pool effectively buffers flow fluctuations, balances temperature, and mixes influent from different sources, greatly improving the stability of CFRO system operation, especially suitable for operating conditions with large fluctuations in water quality and quantity; the intelligent control system monitors and adjusts temperature, pressure, and flow rate in real time, effectively suppressing operating condition fluctuations and ensuring long-term stable operation of the system.

[0016] 5. This invention can significantly reduce overall operating costs, resulting in substantial economic benefits; energy consumption is reduced by more than 30% compared to DTRO / UHPRO; the high concentration ratio significantly reduces the volume of concentrate requiring final treatment, greatly reducing the expensive costs of transporting or disposing of brine; the extended membrane life reduces replacement frequency and maintenance costs; the overall treatment cost in Example 1 can be as low as approximately US$0.43 / m³. 3 It produces water and has significant economic competitiveness.

[0017] 6. This invention enables efficient heat energy recovery and utilization; the waste heat of CFRO high-temperature concentrate is recovered through a heat exchanger for preheating SWRO concentrate; the operating temperature of CFRO is increased, the membrane water flux is enhanced, and the overall heating energy consumption of the system is reduced, thus achieving closed-loop utilization of heat energy. Attached Figure Description

[0018] Figure 1 is a flowchart of the reverse osmosis membrane concentration method of the present invention; in Figure 1: 1, pretreatment system; 2, nanofiltration desalination system; 3, seawater reverse osmosis system (SWRO); 4, heat exchange system; 5, water volume regulating tank; 6, reverse osmosis membrane concentration system (CFRO); 7, pressure energy recovery device. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1Please refer to Figure 1. A CFRO-based countercurrent reverse osmosis membrane concentration method includes the following steps: Step 1: Pretreatment; The raw wastewater S1 first enters the pretreatment system 1, where suspended solids, colloidal impurities, and some organic pollutants are removed through coagulation, sedimentation, and filtration to obtain relatively clean pretreated effluent S2, so as to ensure the stable operation of the subsequent membrane system.

[0021] Step 2: Nanofiltration desalination; the pretreated effluent S2 enters the nanofiltration desalination system 2, where divalent ions are retained to obtain nanofiltration concentrate S3 and nanofiltration permeate S4. The nanofiltration concentrate S3 is used as feed water and concentrate discharge water for subsequent seawater reverse osmosis (SWRO) systems, thereby significantly reducing the risk of scaling and improving the operational stability of subsequent CFRO systems.

[0022] Step 3: Seawater reverse osmosis concentration; Nanofiltration concentrate S3 enters the seawater reverse osmosis system SWRO 3, and is concentrated to the concentration endpoint through high-pressure reverse osmosis treatment to obtain SWRO concentrate S5 and SWRO permeate S6. SWRO concentrate S5 is used as a high-salt and high-pressure fluid to enter the next stage of thermal energy optimization.

[0023] Step 4: Heat exchange; SWRO concentrate S5 and high-temperature concentrate stream S10 from CFRO membrane concentration system 6 exchange heat in heat exchange system 4, and the heat of CFRO concentrate S8 is recovered to preheat SWRO concentrate S7.

[0024] Step 5: Water flow adjustment; After heat exchange, SWRO concentrate S7 and CFRO concentrate S8 are mixed together and enter the water flow adjustment tank 5 to achieve buffering, pressure stabilization, mixing and temperature adjustment, and obtain the effluent S9 from the tank. The water flow adjustment tank 5 provides the CFRO system with uniform and stable influent water in terms of temperature and flow rate, which is conducive to the stable operation of the membrane system.

[0025] Step 6: Countercurrent reverse osmosis high-concentration; the effluent S9 from the integrated tank enters the countercurrent reverse osmosis membrane concentration system CFRO 6 for further high-concentration membrane operation, obtaining CFRO permeate S11 and CFRO concentrate S12; CFRO permeate S11 is recycled for internal system cleaning or partially discharged, and the CFRO concentrate S12 is separated into a high-temperature concentrate stream S10 by the temperature control system and enters the heat exchanger. The remaining unutilized and high-pressure concentrate S13 after reaching the concentration endpoint enters the pressure energy recovery stage.

[0026] Step 7: Pressure energy recovery; High-pressure concentrate S13 enters the pressure energy recovery device 7, and the remaining pressure energy in the high-pressure concentrate S13 is transferred to the CFRO feed water pump or used for other pressurized units in the system, and finally the waste liquid S14 is discharged, so as to further reduce the overall energy consumption of the system.

[0027] Furthermore, the CFRO 6 countercurrent reverse osmosis membrane concentration system adopts a countercurrent operation mode for concentrate and feed water, and combines it with a cross-flow design to improve membrane shear force, reduce fouling, and enhance concentration driving force.

[0028] Among them, the CFRO 6 reverse osmosis membrane concentration system utilizes an external permeation aid to regulate the osmotic pressure gradient across the membrane, which can effectively reduce operating pressure and achieve high-concentration ratios under medium and low pressure conditions.

[0029] Among them, the CFRO 6 countercurrent reverse osmosis membrane concentration system adopts a segmented series multi-effect countercurrent structure. Each segment can independently adjust the inlet and outlet flow rates and osmotic pressure matching state, which can achieve efficient concentration in stages and improve the system's adaptability and scalability.

[0030] Among them, the CFRO 6 countercurrent reverse osmosis membrane concentration system is designed as a high-salt-tolerant membrane system with TDS >100,000 mg / L. The system is designed to directly treat high-salt wastewater or concentrated reflux liquid, breaking through the upper limit of TDS treatment of traditional RO systems and significantly expanding the application range of membrane concentration.

[0031] Furthermore, nanofiltration system 2 separates monovalent and divalent ions, with the nanofiltration membrane in system 2 retaining divalent Ca ions in the water. 2+ Mg 2+ SO4 2- Na+ monovalent ion + Cl - It penetrates nanofiltration membranes; removes easily scale-forming ions such as calcium, magnesium, and sulfate in advance, reduces the scaling pressure on subsequent RO / CFRO membranes, improves the system's anti-fouling ability and concentration stability, and extends membrane life.

[0032] Furthermore, the nanofiltration membrane is an aromatic polyamide composite nanofiltration membrane or a sulfonated polyethersulfone nanofiltration membrane.

[0033] Furthermore, the coagulant added during the coagulation process of the pretreatment system 1 is one or more of polyaluminum chloride, polyferric sulfate, or polyacrylamide.

[0034] Furthermore, flow meters and thermometers are installed in all permeate and concentrate flow paths of the seawater reverse osmosis system SWRO3 and the countercurrent reverse osmosis membrane concentration system CFRO6. Data is collected and analyzed through the control platform, and the temperature control system and flow regulation device are adjusted in a coordinated manner, which can effectively suppress fluctuations in operating conditions and ensure long-term stable operation of the system.

[0035] Furthermore, the operating pressure of the seawater reverse osmosis system SWRO 3 is 50-70 bar, and the operating pressure of the countercurrent reverse osmosis membrane concentration system CFRO 6 does not exceed 83 bar.

[0036] Furthermore, the heat exchange system 4 uses a shell-and-tube heat exchanger or a plate heat exchanger, and the pressure energy recovery device 7 is a pressure exchanger, a hydraulic turbine, or an energy recovery pump; it efficiently recovers the residual pressure energy of the concentrate and feeds it back to the water inlet system or pump set, significantly reducing the load on the high-pressure pump, realizing a closed-loop energy cycle, and improving the system's energy efficiency ratio.

[0037] Furthermore, the overall recovery rate of high-salinity wastewater treated by the countercurrent reverse osmosis membrane concentration method reaches 50%-99.6%, with energy consumption per unit of produced water as low as 5.0 kWh / m³. 3 .

[0038] This invention relates to a countercurrent reverse osmosis membrane concentration system based on a CFRO structure, combined with a specially designed high-pressure-resistant membrane module. Under operating pressure not exceeding 83 bar, it can achieve a maximum concentration of 260,000 mg / L TDS, breaking through the technical bottlenecks of conventional RO and UHPRO technologies in the treatment of high-concentration wastewater. This system not only significantly reduces energy consumption but also possesses excellent fouling resistance and operational stability, making it suitable for various high-salinity wastewater concentration and near-zero discharge (ZLD) scenarios.

[0039] Furthermore, the loss of heat and pressure energy during membrane concentration is a significant factor affecting the overall energy efficiency of the system. Therefore, this invention also proposes integrating the membrane concentration unit with heat and pressure energy recovery devices to achieve high-efficiency operation of the membrane system. By rationally designing the thermal coupling and energy recovery paths, the energy consumption per unit of produced water can be further reduced, the system concentration ratio can be increased, and the long-term stable operation of the membrane system under high concentration and high load conditions can be ensured.

[0040] Example 2 This invention's CFRO-based countercurrent reverse osmosis membrane concentration method also employs an ultra-high pressure reverse osmosis (UHPRO) system to replace the CFRO system. The UHPRO system can operate at pressures up to 120 bar and has the capability to concentrate high-salinity wastewater to 125,000~130,000 mg / L TDS, similar in function to CFRO. However, its main disadvantages are high equipment investment, significant membrane compaction effect, and high operational safety risks. Therefore, in scenarios where higher pressure tolerance or moderate concentration ratio requirements are necessary, UHPRO can serve as an alternative to CFRO.

[0041] Countercurrent reverse osmosis (CFRO) membrane thickening systems can employ multi-stage medium-pressure RO systems connected in series. By operating two or three stages of medium-pressure RO systems in series and using intermediate pressurization or concentrate reuse between stages, similar thickening effects to CFRO can be achieved. Provided water quality conditions permit and membrane fouling is well controlled, this method reduces the maximum pressure requirement of the unit system and simplifies some structural designs. For higher modularity requirements, multi-stage parallel RO systems can be used, with each stage configured with pretreatment and partial recirculation, progressively thickening instead of a CFRO series system. Although the overall energy efficiency is slightly lower, it achieves similar effects by progressively increasing TDS and the thickening rate, and offers greater flexibility in maintenance and management.

[0042] A membrane distillation (MD) coupled system with CFRO can also be added. After CFRO is concentrated to a high TDS level, if a higher concentration ratio or near-zero emissions are required, the CFRO concentrate can be further processed by introducing a membrane distillation (MD) unit at the back end. This combined solution can achieve concentrations of over 200,000 mg / L while maintaining low energy consumption, and it has good integration compatibility.

[0043] CFRO can also be used in combination with freeze crystallization and evaporation crystallization. For the goal of resource utilization of high-concentration brine, CFRO can be used in combination with freeze crystallization or multi-effect evaporation crystallization devices. At the front end, CFRO completes most of the water removal and volume reduction, while at the back end, inorganic salts are recovered and purified, thereby improving the overall resource utilization rate of the system.

[0044] Bypass pumps and automatic regulating valves can also be used to replace the water volume regulating tank. In the absence of a water volume regulating tank, the flow rate and temperature can be dynamically balanced by setting up an inlet bypass pump group + automatic regulating valve + online flow and temperature monitoring system to ensure the stability of the CFRO system's inlet water. This is also suitable for wastewater treatment scenarios with multiple water sources or large fluctuations.

[0045] CFRO membrane segment operation can also be optimized to replace energy coupling measures. By setting up multi-stage CFRO or intermediate pressurization with different pressure differentials, the concentration ratio can be increased without the need for additional energy recovery devices, thereby indirectly achieving energy efficiency optimization.

[0046] Table 1 below compares the results of high-salinity wastewater concentration treatment using the methods described in Examples 1 and 2 of this method, along with traditional RO systems, ultra-high pressure reverse osmosis (UHPRO), multi-effect evaporation (MED), and mechanical vapor recompression (MVR) methods: Table 1 Comparison of High-Salinity Wastewater Concentration Treatment Results As can be seen from the table above: UHPRO is suitable for brackish water and seawater with TDS below 130,000 mg / L, with moderate equipment investment, moderate operation and maintenance complexity, and moderate energy consumption; while evaporators can treat high-salinity water with TDS as high as 260,000 mg / L, their capital expenditure and energy consumption are very high, the system is complex, and the operation and maintenance are difficult; while CFRO also has the ability to treat TDS up to 260,000 mg / L, is suitable for brackish water and high-salinity water, and has advantages such as low to moderate investment cost, simple system structure, convenient operation and maintenance, and moderate energy consumption, making it an ideal choice that combines concentration capacity and economy.

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. A countercurrent reverse osmosis membrane concentration method based on CFRO, characterized in that, Includes the following steps: Step 1: Pretreatment; The raw wastewater S1 first enters the pretreatment system (1), where suspended solids, colloidal impurities and some organic pollutants are removed through coagulation, sedimentation and filtration to obtain pretreated effluent S2; Step 2: Nanofiltration desalination; Pretreated effluent S2 enters the nanofiltration desalination system (2) to retain divalent ions, obtaining nanofiltration concentrate S3 and nanofiltration permeate S4. Nanofiltration concentrate S3 is used as feed water for subsequent seawater reverse osmosis (SWRO). Step 3: Seawater reverse osmosis concentration. Nanofiltration concentrate S3 enters the seawater reverse osmosis system SWRO (3), and is concentrated to the concentration endpoint through high-pressure reverse osmosis treatment, obtaining SWRO concentrate S5 and SWRO permeate S6. SWRO concentrate S5 is used as a high-salt, high-pressure fluid to enter the next stage of thermal energy optimization. Step 4: Heat exchange. SWRO concentrate S5 and high-temperature concentrate S10 from the countercurrent reverse osmosis membrane concentration system CFRO (6) undergo heat exchange in the heat exchange system (4), and the heat from CFRO concentrate S8 is recovered to preheat SWRO concentrate S7; Step 5: Water flow adjustment; After heat exchange, SWRO concentrate S7 and CFRO concentrate S8 are mixed together and enter the water flow adjustment pool (5) to achieve buffering, pressure stabilization, mixing and temperature adjustment, and obtain pool effluent S9; Step 6: Countercurrent reverse osmosis high-concentration; Pool effluent S9 enters the countercurrent reverse osmosis membrane concentration system CFRO (6) for further high-concentration. Membrane concentration operation to obtain CFRO permeate S11 and CFRO concentrate S12; CFRO permeate S11 is recovered for internal system cleaning or partially discharged externally, and CFRO concentrate S12 is separated into high-temperature concentrate S10 by the temperature control system and enters the heat exchanger. The remaining high-pressure concentrate S13, which is not fully utilized and reaches the concentration endpoint, enters the pressure energy recovery stage; Step 7: Pressure energy recovery; High-pressure concentrate S13 enters the pressure energy recovery device (7) to transfer the remaining pressure energy in high-pressure concentrate S13 to the CFRO feed pump or for other pressurized units in the system, and finally discharges waste liquid S14.

2. The method for countercurrent reverse osmosis membrane concentration based on CFRO according to claim 1, characterized in that, The countercurrent reverse osmosis membrane concentration system CFRO (6) adopts a countercurrent operation mode of concentrate and feed water, combined with cross-flow design, and uses external osmotic aid to regulate the osmotic pressure gradient on both sides of the membrane; the countercurrent reverse osmosis membrane concentration system CFRO (6) adopts a segmented series multi-effect countercurrent structure, and each segment independently adjusts the inlet and outlet flow rates and osmotic pressure matching state; the countercurrent reverse osmosis membrane concentration system CFRO (6) is designed as a high salt tolerance membrane system with TDS >100,000 mg / L.

3. The method for countercurrent reverse osmosis membrane concentration based on CFRO according to claim 1, characterized in that, The nanofiltration desalination system (2) separates monovalent and divalent ions. The nanofiltration membrane in the nanofiltration desalination system (2) retains divalent ions Ca2+ in the water. 2 + Mg 2+ SO4 2- Monovalent Na+ + Cl - Penetrates nanofiltration membrane.

4. The method for countercurrent reverse osmosis membrane concentration based on CFRO according to claim 3, characterized in that, The nanofiltration membrane is an aromatic polyamide composite nanofiltration membrane or a sulfonated polyethersulfone nanofiltration membrane.

5. The method for countercurrent reverse osmosis membrane concentration based on CFRO according to claim 1, characterized in that, The coagulant added during the coagulation process of the pretreatment system (1) is one or more of polyaluminum chloride, polyferric sulfate, or polyacrylamide.

6. The method for countercurrent reverse osmosis membrane concentration based on CFRO according to claim 1, characterized in that, Flow meters and thermometers are installed in all product water and concentrate flow paths of the seawater reverse osmosis system SWRO (3) and the countercurrent reverse osmosis membrane concentration system CFRO (6). Data is collected and analyzed through the control platform, and the temperature control system and flow regulation device are adjusted in a coordinated manner.

7. The method for countercurrent reverse osmosis membrane concentration based on CFRO according to claim 1, characterized in that, The operating pressure of the seawater reverse osmosis system SWRO (3) is 50-70 bar, and the operating pressure of the countercurrent reverse osmosis membrane concentration system CFRO (6) does not exceed 83 bar.

8. The method for countercurrent reverse osmosis membrane concentration based on CFRO according to claim 1, characterized in that, The heat exchange system (4) is selected from shell-and-tube heat exchangers or plate heat exchangers, and the pressure energy recovery device (7) is a pressure exchanger, a hydraulic turbine or an energy recovery pump.

9. The method for countercurrent reverse osmosis membrane concentration based on CFRO according to claim 1, characterized in that, The overall recovery rate of high-salinity wastewater treated by the countercurrent reverse osmosis membrane concentration method reaches 50%-99.6%, with energy consumption per unit of produced water as low as 5.0 kWh / m³. 3 .

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