Reverse osmosis pure water production method and equipment based on synergistic purification of two-stage membrane modules

Abstract

This invention discloses a reverse osmosis pure water production method and equipment based on the synergistic purification of a two-stage membrane module, relating to the field of wastewater treatment technology. In the water quality monitoring stage after pretreatment, this invention performs preliminary feed water optimization on the desalination process of the reverse osmosis module based on acquired ion migration state data to reduce the scaling rate on the reverse osmosis membrane surface. Then, based on the salinity of the feed water at the inlet corresponding to the first-stage reverse osmosis membrane after the preliminary feed water optimization, pressure-flow rate synergistic control is implemented for the pressure fine desalination process of the first-stage reverse osmosis membrane, while simultaneously adjusting the circulation flow rate. Finally, based on the conductivity at a designated location within the feed water buffer tank of the first-stage reverse osmosis membrane, and combined with the feedback status of the permeate water quality from the second-stage reverse osmosis membrane, the feed water parameters of the reverse osmosis module are adjusted. This achieves refined, adaptive, and synergistic control of the reverse osmosis module, effectively solving the problem of desalination efficiency fluctuations caused by pressure difference changes in the application of two-stage membranes in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a reverse osmosis pure water production method and equipment based on the synergistic purification of two-stage membrane modules. Background Technology

[0002] In the pure water production process, the core of the pure water production equipment consists of filters, ion exchange membranes, precision filters, reverse osmosis (RO) membranes, and a dilute acid and alkali collection and transportation structure. After receiving raw water, it first enters the filtration and storage tank for pretreatment. Through hydrolysis, hydrogen ions and hydroxide ions are generated. These ions can adjust the pH value of the raw water, stabilizing it within the optimal range for subsequent filtration processes. Simultaneously, substances in the raw water that easily cause membrane fouling are guided to specific areas, where they are converted into easily treatable forms and retained, thus completing the pretreatment of the raw water. The pretreated water then enters the RO membrane feed buffer tank through pipelines and is transported to the reverse osmosis membrane for fine desalination. Pressure is applied to drive the water flow through the reverse osmosis membrane. During this process, remaining impurities in the water are retained by the reverse osmosis membrane, allowing only water molecules to pass through smoothly, achieving deep desalination and ultimately producing high-purity pure water. A valve is used to return a portion of the water that has passed through the RO membrane to the feed end to reduce the salt content. In addition, dilute acids and alkalis are generated during operation, and Joule heat is also generated during the electric field-driven ion migration process. These substances are introduced into a special membrane cleaning cycle process, while the heat is collected by using a heat-conducting medium to compensate for temperature deviations in the future. The equipment purifies water through the process of raw water → raw water tank → raw water pump → multi-media filter → activated carbon filter → softener → primary precision filter → secondary precision filter → fresh water chamber → inlet buffer tank → primary reverse osmosis → secondary reverse osmosis → purified water tank → pure water pump → point of use.

[0003] For example, Chinese invention patent CN104230076B discloses a method for treating reverse osmosis concentrate during urban wastewater reuse. The method includes: adjusting the pH value of the reverse osmosis concentrate and heating it to a certain temperature, then conveying it to a hydrophobic membrane module for concentration treatment; using a vacuum method to condense the permeated steam to form permeate, which is used for direct reuse or mixed with reverse osmosis permeate for reuse; using a partial concentrate circulation method to concentrate the generated concentrate and send it to a gravity sedimentation separator for classification; the supernatant after separation enters a microfiltration membrane unit to remove suspended solids, while the wastewater containing a large amount of suspended solids undergoes solid-liquid separation, and the separated mother liquor is sent to a spray drying unit for drying treatment.

[0004] For example, Chinese invention patent CN105417898B discloses a method for treating reverse osmosis concentrate and ultrafiltration backwash water in a dual-membrane system. The method includes: using a pre-coated membrane to resist ultrafiltration membrane fouling, and a comprehensive treatment method combining aerobic tank treatment of zeolite powder and ozone treatment of reverse osmosis concentrate to treat the ultrafiltration membrane and reverse osmosis process. In the ozone treatment process, hydrogen peroxide and ozone are optimally controlled. The treated wastewater enters the front-end biological recycling treatment of a wastewater treatment plant to remove pollutants such as COD and ammonia nitrogen. The adsorbent material of the ultrafiltration membrane system is pre-coated zeolite powder.

[0005] The above-mentioned technology has at least the following technical problems:

[0006] In existing technologies, during the raw water purification process, the stable operation of the reverse osmosis membrane needs to be adapted to the salinity of the feed water. Its operating parameters need to be dynamically adjusted according to the real-time changes in the total dissolved solids and salinity of the current water body. When the salinity of the raw water fluctuates due to the mixing of more high-salinity sources in the water source or a sudden failure of the pre-filtration (such as resin softening failure), the pre-filter components (such as precision filters) cannot completely suppress the fluctuations. In short-term sudden fluctuations such as heavy rain causing an increase in the total dissolved solids of the raw water, the pretreatment steps cannot treat the large volume of high-salinity water in time. At this time, the membrane surface is overloaded with impurities, which causes the pressure difference between the inlet and outlet of the reverse osmosis membrane to rise faster. There is a problem of a high rate of change in the pressure difference between the inside and outside of the two-stage reverse osmosis membrane during the reverse osmosis process. Summary of the Invention

[0007] To address the technical problem of high pressure difference variation rates across the two-stage reverse osmosis membranes in existing reverse osmosis technologies, this invention provides a reverse osmosis pure water production method and equipment based on synergistic purification using two-stage membrane modules. The technical solution is as follows:

[0008] On the one hand, a reverse osmosis pure water production method based on synergistic purification of two-stage membrane modules is provided. This method is implemented using a reverse osmosis pure water production device with synergistic purification of two-stage membrane modules, and includes:

[0009] Step 1: In the water quality monitoring stage after pretreatment, the feed water of the reverse osmosis module is initially optimized based on the acquired ion migration status data to reduce the scaling rate on the reverse osmosis membrane surface. The initial feed water optimization includes ion membrane switching and cleaning status control. The reverse osmosis module includes a freshwater chamber containing an ion exchange membrane, a primary reverse osmosis membrane, and a secondary reverse osmosis membrane. Step 2: Based on the feed water salinity at the inlet of the primary reverse osmosis membrane after the initial feed water optimization, the pressure-flow rate coordinated control of the pressure fine desalination process of the primary reverse osmosis membrane is implemented, while the circulation flow rate is adjusted to reduce the deposition of residual pollutants on the membrane surface. Step 3: Based on the conductivity at a designated location within the feed water buffer tank of the primary reverse osmosis membrane, and combined with the feedback status of the permeate water quality from the secondary reverse osmosis membrane, the feed water parameters of the reverse osmosis module are adjusted to reduce concentration polarization and membrane fouling caused by the feed water flow rate at the inlet of the primary reverse osmosis membrane. The feed water parameters include electric field strength and feed water salinity.

[0010] On the other hand, a reverse osmosis pure water production equipment based on the synergistic purification of two-stage membrane modules is provided. This equipment is applied to the reverse osmosis pure water production method based on the synergistic purification of two-stage membrane modules. The equipment includes: a preliminary filter device, a precision filter device, a freshwater conditioning device, and a two-stage reverse osmosis device.

[0011] The preliminary filtration device includes a preliminary filter for preliminary filtration of raw water and a flow meter for detecting flow rate and velocity; the precision filtration device includes a precision filter for tight filtration of the water after preliminary filtration, a flow sensor for detecting flow rate and velocity, and a turbidity sensor for detecting the content of solid particles in the water; the freshwater conditioning device includes a flow sensor for detecting the flow rate at the inlet and outlet of the freshwater chamber, a voltage sensor for detecting the voltage value of electrolytic conditioning in the freshwater chamber, a pH sensor for detecting the pH value before and after freshwater conditioning, and a conductivity sensor for detecting the salinity of the water in the buffer tank; the two-stage reverse osmosis device includes a flow sensor for detecting the flow rate and velocity corresponding to the first-stage and second-stage reverse osmosis membranes, a pressure sensor for detecting the deviation between the water pressure and membrane flux pressure of the two-stage reverse osmosis membranes, and a conductivity sensor for detecting the conductivity of the feed water and product water of the two-stage reverse osmosis membranes.

[0012] The beneficial effects of the technical solutions provided by the embodiments of the present invention include at least the following:

[0013] 1. Based on the preliminary feed water optimization of ion migration status and the synergistic design of the ion exchange membrane desalination chamber and the two-stage reverse osmosis membrane, the feed water is classified into three categories according to the initial pH value in the desalination chamber. When the pH value is higher than the preset range, the focus is on monitoring the migration status of anions to enhance the migration efficiency of cations and reduce the feed water pH. When the pH value is lower than the preset range, the focus shifts to monitoring the migration status of cations to enhance the migration of anions and raise the feed water pH. When the pH is within the acceptable range, the operating conditions are maintained to ensure stability. This approach matches classification judgment with migration status monitoring, ion type adaptation with dynamic adjustment of electric field strength, so that the ion exchange membrane desalination chamber guides scale-prone ions away from the mainstream feed water through directional ion migration, reducing their probability of entering the subsequent RO components. By using ion migration status data to guide the preliminary feed water optimization of the RO components, the water entering the first-stage RO not only has a stable pH but also reduces the content of scale-prone ions, thus reducing the probability of scaling on the RO membrane surface from the source.

[0014] 2. Pressure-flow rate coordinated control based on feed water salinity: Taking the salinity in the primary RO feed water buffer tank as the core basis, flow rate control is synchronously linked during the pressure-based desalination process. When the feed water salinity exceeds the upper limit, the membrane shear force is increased to prevent salt accumulation on the membrane surface. When the feed water salinity is below the lower limit, the pressure reduction step is calculated to reduce energy consumption, while maintaining or fine-tuning the flow rate to ensure water production efficiency. When the feed water salinity is stable, the current pressure is maintained, and the osmotic pressure difference between the inlet and outlet is monitored in real time. Through dynamic adaptation of pressure and flow rate, the desalination rate can be guaranteed by increasing pressure when the salinity is higher than the preset value, and concentration polarization can be avoided by optimizing the flow rate. When the salinity is lower than the preset value, energy consumption is saved by reducing pressure, while water production is guaranteed by stabilizing the flow rate. When the pipeline is blocked, the flow rate is not forcibly maintained by high pressure, but the blockage problem is solved by adjusting the flow rate to avoid membrane damage.

[0015] 3. By implementing cross-membrane linkage control of the cleaning status, the cleaning of ion exchange membranes and RO membranes are deeply integrated. Simultaneously, the reuse logic of the cleaning solution is optimized, achieving a dual improvement in cleaning efficiency and resource utilization of the two-stage membrane modules. The ion exchange membrane cleaning status control is based on the pH value of the freshwater outlet. When the pH deviates, the subsequent scaling efficiency is reduced by shortening the circulation time, providing a basis for adjusting the RO membrane circulation flow rate. Flow rate optimization reduces the probability of scaling on the RO membrane surface. Simultaneously, it determines whether the cleaning solution concentration meets the standard: if it does, a reflux command is sent to reuse the cleaning solution; if not, a waste command is sent to discharge it into wastewater treatment. The cleaning effect of the ion exchange membrane directly guides the flow rate adjustment of the RO membrane, avoiding the risk of RO scaling due to incomplete ion exchange membrane cleaning.

[0016] 4. By optimizing the feed water parameters driven by the synergistic desalination index, a quantitative evaluation system for the synergistic efficiency of the two-stage RO system was constructed. Based on this index, the electric field strength and feed water salinity were dynamically adjusted to achieve precise control of deep desalination and energy consumption balance. The overall desalination synergistic efficiency of the two-stage RO system was quantified by combining the first and third conductivity values. If the synergistic desalination index exceeds the upper limit, desalination is enhanced by improving ion migration efficiency. If the index is below the lower limit, the electric field strength of the membrane stack is reduced to lower energy consumption, and the feed water buffer tank flow rate is adjusted simultaneously. The synergistic desalination index allows for a direct assessment of the overall synergistic effect of the two-stage RO system, avoiding overall efficiency imbalances caused by single-stage parameter optimization. The linkage adjustment of electric field strength and feed water salinity not only addresses desalination failure issues but also reduces energy consumption while ensuring effective desalination. The combination of waste heat compensation and reflux regulation further ensures the stability of feed water temperature and salinity.

[0017] 5. Through voltage-flow matching control of the freshwater chamber, based on the preset voltage-flow matching curve, the electrolysis voltage and the influent flow rate are dynamically and synchronously adjusted to optimize ion migration efficiency and ensure the stability of RO influent. When the electrolysis voltage increases relative to the set value, the decrease in the speed of the influent variable frequency pump is calculated through the voltage-flow matching curve, and the influent flow rate is reduced to extend the hydraulic residence time of ions in the freshwater chamber. When the flow rate decreases, the speed increases. Through the synchronous adjustment of voltage and flow rate, incomplete desalination caused by insufficient residence time of ions under high voltage is avoided, and efficiency waste caused by excessive residence time under low voltage is also prevented. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the reverse osmosis pure water production method based on synergistic purification of a two-stage membrane module provided in an embodiment of the present invention;

[0020] Figure 2 The flowchart for optimizing the initial feed water for reverse osmosis provided in this embodiment of the invention;

[0021] Figure 3 The flowcharts for pressure-flow rate coordinated circulation adjustment and reverse osmosis feed water parameter adjustment provided in the embodiments of the present invention are shown. Detailed Implementation

[0022] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0023] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0024] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0025] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0026] This invention provides a reverse osmosis pure water production method based on synergistic purification using a two-stage membrane module. This method can be implemented using a reverse osmosis pure water production device based on synergistic purification using a two-stage membrane module. Figure 1 The flowchart shown illustrates a reverse osmosis pure water production method based on synergistic purification using a two-stage membrane module. The process can include the following steps: Step 1: In the water quality monitoring stage after pretreatment, preliminary feed water optimization is performed on the desalination process of the reverse osmosis module based on the acquired ion migration state data to reduce the scaling rate on the reverse osmosis membrane surface. Preliminary feed water optimization includes ion membrane switching and cleaning status control. The reverse osmosis module includes a freshwater chamber containing an ion exchange membrane, a primary reverse osmosis membrane, and a secondary reverse osmosis membrane; Step 2: Based on the preliminary feed water optimization, at the inlet of the primary reverse osmosis membrane... The feed water salinity is used to control the pressure-flow rate of the first-stage reverse osmosis membrane during pressure fine desalination, while adjusting the circulation flow rate to reduce the deposition of residual pollutants on the membrane surface. Step 3: Based on the conductivity at a designated location in the feed water buffer tank of the first-stage reverse osmosis membrane, and combined with the feedback status of the permeate water quality of the second-stage reverse osmosis membrane, the feed water parameters of the reverse osmosis module are adjusted to reduce concentration polarization and membrane fouling caused by the feed water flow rate at the inlet of the first-stage reverse osmosis membrane, thereby stabilizing the permeate water quality and improving the pure water recovery rate. The feed water parameters include electric field strength and feed water salinity.

[0027] In a specific embodiment, for example, in the process of purifying pure water for food and pastry, the pretreatment stage can only remove basic impurities and does not dynamically adjust the treatment strategy in conjunction with the ion migration state. The parameters such as pressure and flow rate of the reverse osmosis system cannot be coordinated with the salinity of the feed water and the quality of the product water in real time. Occasionally, the quality of the product water fluctuates, which may affect the stability of the dough during the pastry making process.

[0028] When raw water enters the pure water production process, the pretreatment stage will conduct preliminary feed water optimization based on ion migration status data. Through ion membrane switching and cleaning status control, easily scale-forming ions are guided away from the main feed water channel, reducing the probability of these ions entering the subsequent reverse osmosis components, thereby helping to reduce scaling on the surface of the reverse osmosis membrane.

[0029] After entering the first-stage reverse osmosis stage, based on the initially optimized feed water salinity, the system implements pressure-flow rate coordinated control for the pressure-based fine desalination process, while simultaneously adjusting the circulation flow rate to effectively reduce the deposition of residual contaminants on the surface of the first-stage reverse osmosis membrane. Subsequently, by combining the conductivity within the first-stage reverse osmosis membrane feed water buffer tank with feedback from the second-stage reverse osmosis membrane's permeate water quality, the electric field strength of the reverse osmosis components and the feed water salinity are adjusted to further reduce concentration polarization and membrane fouling caused by issues with the first-stage reverse osmosis membrane feed water flow rate. Ultimately, this ensures stable permeate water quality throughout the system, while also contributing to improved pure water recovery rates and guaranteeing continuous and stable system operation.

[0030] like Figure 2 The flowchart shown is a flowchart of the initial feed water optimization for reverse osmosis provided in an embodiment of the present invention. First, the feed water is classified, and after the classification, the pH value of the outlet is monitored. The range of the initial pH value of the feed water is determined to adjust the electric field strength, voltage, and maintain the current value. The pH value monitoring of the outlet is based on the obtained pH value to determine the range, so as to adjust the electrolysis voltage and match the feed water flow. After the feed water flow is matched, the cleaning status control is performed, which includes the cleaning status control of the ion exchange membrane and the cleaning status control of the reverse osmosis membrane.

[0031] Furthermore, preliminary feed water optimization is performed on the desalination process of the reverse osmosis module. Specifically, the feed water is initially categorized based on its initial pH value in the freshwater chamber: First category: If the initial pH value in the freshwater chamber is greater than the maximum value of the preset feed water range, the anion migration state in the freshwater chamber is monitored, and a cation exchange membrane switching command is sent to prompt personnel to check the current ion exchange membrane and lower the pH value of the feed water in the freshwater chamber; if the current freshwater chamber is in a cation migration state, the electric field strength is increased based on the current cation migration rate to enhance cation migration efficiency; Second category: If the initial pH value in the freshwater chamber is within the preset feed water range... If the pH value is within the specified range, it indicates that the working status of the first-stage reverse osmosis membrane is qualified and the current pH value is maintained. In the third category, if the initial pH value in the freshwater chamber is less than the minimum value of the preset feed water range, the cation migration status in the freshwater chamber is monitored, and an anion membrane switching command is sent to prompt the preset personnel to check the current ion exchange membrane and increase the pH value of the feed water in the freshwater chamber. If the current freshwater chamber is in anion migration state, the voltage increase value on both sides of the ion exchange membrane is obtained based on the current anion migration rate through the ion-electric field mapping relationship to enhance the driving force of the electric field on the ions. After monitoring the ion migration status in the freshwater chamber, the pH value of the freshwater chamber outlet is monitored.

[0032] Specifically, pH monitoring at the freshwater chamber outlet is performed as follows: If the pH value at the freshwater chamber outlet is greater than the maximum value of the preset inlet range, the pH value deviation at the outlet is input into the RO optimal-electrolysis voltage mapping relationship to obtain an increase in the electrolysis voltage within the freshwater chamber, thereby increasing the migration rate of anions to the acid chamber. The pH value deviation at the outlet represents the difference between the obtained pH value at the freshwater chamber outlet and the maximum value of the preset inlet range. If the pH value at the freshwater chamber outlet is less than the minimum value of the preset inlet range, the pH value deviation at the outlet is input into the RO optimal-electrolysis voltage mapping relationship to obtain a decrease in the electrolysis voltage within the freshwater chamber, thereby reducing the migration rate of cations to the alkaline chamber. The pH value deviation at the outlet represents the difference between the obtained pH value at the freshwater chamber outlet and the maximum value of the preset inlet range. The difference between the minimum and maximum values; if the pH value at the outlet of the freshwater chamber is within the preset inlet range, the current electrolysis voltage is maintained, and the inlet flow rate of the freshwater chamber is matched with the electrolysis voltage. Specifically: if the current electrolysis voltage increases relative to the set electrolysis voltage, the operating speed of the inlet variable frequency pump is reduced according to the preset voltage-flow matching curve, and the flow rate is reduced to extend the hydraulic residence time of the ion water; if the current electrolysis voltage decreases relative to the set electrolysis voltage, the operating speed of the inlet variable frequency pump is increased according to the preset voltage-flow matching curve, and the flow rate is increased to reduce the hydraulic residence time; the voltage-flow matching curve is used to visualize the mapping relationship between the corresponding electrolysis voltage and the inlet flow rate during the electrolytic water treatment process. When the electrolysis voltage is adjusted, the adjustment value of the inlet flow rate is obtained synchronously through this curve.

[0033] Specifically, the cleaning status control includes cleaning status control for ion exchange membranes to improve electrolysis efficiency and cleaning status control for reverse osmosis membranes to improve reverse osmosis efficiency. Specifically: Ion exchange membrane cleaning status control involves real-time monitoring of the pH value at the outlet of the freshwater chamber corresponding to the ion exchange membrane in the cleaning tank. If the pH value at the outlet is not within the preset outlet range, the pH deviation is input into the ion outlet-circulation time mapping relationship to obtain a reduction in the circulation time of the desalination flow rate, thereby reducing the subsequent scaling efficiency. Reverse osmosis membrane cleaning status control specifically involves: Based on the concentration deviation of the cleaning solution after the ion exchange membrane cleaning status control, the circulation flow rate adjustment value of the dual-stage reverse osmosis membrane is obtained to reduce the probability of scaling on the surface of the dual-stage reverse osmosis membrane. The dual-stage reverse osmosis membrane includes a primary reverse osmosis membrane and a secondary reverse osmosis membrane. The cleaning solution concentration deviation is used to reflect the cleaning degree of the dual-stage reverse osmosis membrane. If the cleaning solution concentration after the reverse osmosis membrane cleaning status control is greater than the preset cleaning solution concentration, a reflux command is sent to recycle the cleaning solution. Otherwise, a cleaning solution waste command is sent to discharge the cleaning solution into wastewater treatment. The cleaning solution concentration includes cleaning acid solution and cleaning alkali solution.

[0034] In this embodiment, the increase in electric field strength and voltage boost value obtained based on ion migration rate are derived from the ion-electric field mapping relationship. This mapping relationship is based on a support vector regression algorithm, which uses ion migration rate data from historical data as input and historical electric field strength and voltage as output for training. The trained model is then embedded, receiving ion migration rate data in real time and outputting the increase in electric field strength or voltage boost value. The preset influent range is the working range of the influent pH value of the first-stage RO membrane in the reverse osmosis module, set according to the reverse osmosis membrane used. The RO optimal-electrolysis voltage mapping relationship is obtained by taking the deviation of the outlet pH value... The deviation is input to the electrolysis voltage controller in the freshwater conditioning unit. The controller adjusts the electrolysis voltage in real time based on the pre-built optimal RO-electrolysis voltage correspondence to adapt to the pH requirements of the reverse osmosis module's feed water. The specific process of building the optimal RO-electrolysis voltage correspondence is as follows: Based on historical operating data, the feed water pH, R0 parameters (such as permeate rate and desalination rate), and electrolysis voltage records of the reverse osmosis module under different operating conditions are extracted; the parameter combinations of R0 performance under each operating condition are screened and associated with the corresponding electrolysis voltage; then, through data fitting and error correction, a callable correspondence library is formed. The following mapping relationship construction process is related to the RO... Similar to the optimal electrolysis voltage mapping relationship, the voltage-flow matching curve is obtained based on the AdaBoost regression algorithm. It uses historical electrolysis voltage as input and flow rate as output for training. The preset effluent range is the stable operating range of the reverse osmosis components during the historical ion exchange membrane cleaning process. The ion effluent-circulation time mapping relationship involves inputting the obtained effluent pH deviation into the circulation pump controller of the freshwater conditioning device. This controller adjusts the circulation time in real time based on the pre-set ion effluent-circulation time correspondence. This pre-set ion effluent-circulation time correspondence is based on... The parameters extracted from historical operating data, the cleaning solution concentration deviation, and the circulation flow rate adjustment value of the two-stage reverse osmosis membrane are obtained through the LightGBM algorithm. The algorithm takes the cleaning solution concentration deviation from historical data as input and the circulation flow rate as output for training. The outlet pH value deviation represents the difference between the obtained outlet pH value and the preset maximum / minimum value of the outlet range. The cleaning solution concentration deviation represents the difference between the cleaning solution concentration before and after the ion exchange membrane cleaning state control. The preset cleaning solution concentration is represented by the summation and average of the historical cleaning solution concentrations in the historical reverse osmosis membrane cleaning state control.

[0035] By classifying and regulating the initial pH value of the freshwater chamber, dynamically adjusting the electric field strength or the voltage across the ion exchange membrane based on the ion migration status, and further optimizing the pH value at the outlet by secondary monitoring and electrolysis voltage, the pH of the freshwater effluent can be stabilized within a range suitable for subsequent reverse osmosis components. This reduces the retention of scale-prone ions and lowers the risk of reverse osmosis membrane scaling at its source. Simultaneously, matching the electrolysis voltage with the freshwater influent flow rate allows for a proper match between the ion hydraulic residence time and the electrolysis driving force, improving ion migration efficiency and ensuring desalination effectiveness.

[0036] In the cleaning status control, the ion exchange membrane optimizes the desalination flow rate and circulation time based on the pH deviation, while the reverse osmosis membrane adjusts the circulation flow rate based on the concentration deviation of the cleaning solution. This can reduce fouling and scaling of both types of membranes, extend the stable operation cycle of the membranes, and reduce reagent waste and wastewater discharge through the reflux and reuse of the cleaning solution, thus balancing treatment effect and resource utilization efficiency.

[0037] like Figure 3 The diagram shows a flowchart of the pressure-flow rate coordinated circulation adjustment and reverse osmosis feed water parameter adjustment provided in the embodiment of the invention. The first conductivity is used to divide the area into intervals to adjust the pressure increase step or pressure decrease step. During the interval division process, the osmotic pressure difference is monitored in real time. The circulation flow rate and the feed water parameters of the two-stage reverse osmosis membrane are adjusted through permeate circulation adjustment. Feed water preheating is adjusted during the feed water parameter adjustment process. The membrane stack electric field strength is increased / decreased by obtaining the coordinated desalination index. At the same time, the reflux flow rate is adjusted based on the opening value of the reflux valve.

[0038] Furthermore, pressure-flow rate coordinated control is implemented for the pressure-based desalination process of the first-stage reverse osmosis membrane. The specific steps are as follows: Based on the salt content in the feed water buffer tank of the first-stage reverse osmosis membrane, a first conductivity is obtained and compared with a preset reverse osmosis conductivity range. If the obtained first conductivity is greater than the maximum value of the preset reverse osmosis conductivity range, an adjustment value for the pressure increase step is obtained based on the deviation of the first conductivity, thereby increasing the water pressure increase of the first-stage reverse osmosis membrane until the first conductivity is within the preset reverse osmosis conductivity range. During the water pressure adjustment process, the conductivity of the permeate after passing through the first-stage reverse osmosis membrane is monitored in real time to obtain a second conductivity. If the water pressure increases to the preset permeate pressure... If the second conductivity is greater than the preset second conductivity of the first-stage reverse osmosis membrane, the water pressure adjustment is paused, and a water conductivity warning command is sent to investigate desalination failure. If the obtained first conductivity is less than the minimum value of the preset reverse osmosis conductivity range, the pressure reduction step size is adjusted based on the deviation of the first conductivity to reduce the water pressure reduction of the first-stage reverse osmosis membrane. If the second conductivity is still less than the preset second conductivity of the first-stage reverse osmosis membrane after the water pressure is reduced, it indicates that the pressure reduction is effective. Otherwise, the high-pressure pump is prompted to return to the water pressure corresponding to the water pressure before the water pressure reduction. The second conductivity represents the conductivity of the permeate obtained by the feed water corresponding to the first conductivity after passing through the first-stage reverse osmosis membrane.

[0039] If the obtained first conductivity is within the preset reverse osmosis conductivity range, it indicates that the salinity of the feed water to the first-stage reverse osmosis membrane is stable, and the current water pressure on the first-stage reverse osmosis membrane is maintained. During the water pressure adjustment process, the osmotic pressure difference between the inlet and the product water outlet is monitored in real time. If the membrane flux pressure deviation is greater than the preset membrane flux pressure deviation, and the water pressure is increased to the preset product water pressure, it indicates that the pipeline is blocked. Based on the currently obtained membrane flux pressure deviation, the increase in the product water circulation velocity is obtained. By increasing the pipeline re-flushing rate, the membrane flux pressure deviation and osmotic pressure difference are reduced. The membrane flux pressure deviation represents the difference between the obtained pressure at the inlet and the product water outlet. After the product water circulation velocity is increased, the membrane flux pressure deviation is obtained again. When the membrane flux pressure deviation is less than the preset membrane flux pressure deviation, the current product water circulation velocity is maintained.

[0040] Specifically, the circulation flow rate is adjusted as follows: Based on the acquired membrane surface water flow rate, it is input into the membrane surface flow rate-concentrate return mapping relationship to obtain the concentrate return rate adjustment value, thereby increasing the concentrate circulation volume. The membrane surface water flow rate is then reacquired. The membrane surface water flow rate and the pressure difference between the inside and outside of the membrane represent the membrane surface water flow rate and the pressure difference between the inside and outside of the membrane corresponding to the first-stage reverse osmosis membrane. If the reacquired membrane surface water flow rate is greater than the preset membrane surface water flow rate, the high-pressure pump frequency is adjusted based on the currently acquired pressure difference between the inside and outside of the membrane to maintain the concentrate flow rate and increase the membrane shear force. Concentrate refers to the water flow that does not pass through the first-stage reverse osmosis membrane, and the pressure difference between the inside and outside of the membrane is the difference between the pressure inside and outside the first-stage reverse osmosis membrane.

[0041] In this embodiment, the preset reverse osmosis conductivity range is a closed interval formed by the maximum and minimum values ​​of the historical first conductivity during the historical pressure-flow rate coordinated control process. The upper deviation of the first conductivity represents the difference between the obtained first conductivity and the maximum value of the preset reverse osmosis conductivity range, and the lower deviation of the first conductivity represents the difference between the obtained first conductivity and the minimum value of the preset reverse osmosis conductivity range. The adjustment value of the pressure increase / decrease step size obtained by the upper / lower deviation of the first conductivity is used to input the obtained upper / lower deviation of the first conductivity into the high pressure of the two-stage reverse osmosis device. In the pump controller, the controller adjusts the pressure increase / decrease step size in real time through a pre-built conductivity-water pressure correspondence. The conductivity-water pressure correspondence is based on historical operating data and pressure adjustment records of the two-stage reverse osmosis unit to obtain a corresponding mapping library. The preset permeate pressure is represented by the summation and averaging of historical permeate pressures in the historical pressure-flow rate coordinated control process. The increase in permeate circulation flow rate is obtained based on the membrane flux pressure deviation. A convolutional neural network algorithm is used to construct the mapping relationship between the membrane flux pressure deviation and the permeate circulation flow rate adjustment value. During the training phase, historical membrane flux pressure deviations are used as input samples, and corresponding permeate circulation velocity adjustment values ​​are used as output samples to train and optimize the convolutional neural network. This enables the model to learn the nonlinear relationship between pressure deviation and velocity adjustment. The preset membrane flux pressure deviation is represented by the summation and averaging of historical membrane flux pressure deviations during historical pressure-velocity coordinated control processes. The membrane surface velocity-concentrate return mapping relationship is obtained by training the model using a support vector regression algorithm, with the input being the membrane surface water flow velocity and the output being the concentrate return rate adjustment value. The preset membrane surface water flow velocity is represented by the summation and averaging of historical membrane surface water flow velocities during historical pressure-velocity coordinated control processes. Based on the currently acquired membrane pressure difference, the high-pressure pump frequency adjustment value is obtained by adjusting the high-pressure pump frequency according to the currently acquired membrane pressure difference and a pre-set pressure difference-frequency correspondence. This correspondence is obtained through data fitting based on historical operating records of the two-stage reverse osmosis unit.

[0042] The pressure regulation and circulation flow rate control of the first-stage reverse osmosis membrane form a closed-loop adaptation that closely matches water quality changes and system conditions. This effectively balances desalination performance, energy consumption control, and membrane module protection, avoiding operational imbalances caused by adjusting a single parameter. By dynamically adjusting the water pressure based on the salinity (primary conductivity) in the first-stage reverse osmosis membrane feed buffer tank and comparing it with a preset range, energy waste caused by excessive pressure can be avoided, as can incomplete desalination due to insufficient pressure. This also prevents the continuous production of substandard permeate and further damage to the membrane module under abnormal conditions.

[0043] During pressure adjustment, the osmotic pressure difference between the inlet and outlet, as well as the membrane flux pressure deviation, are monitored simultaneously. This eliminates the need for forcibly breaking through blockages with high pressure, reducing damage to the pipe walls and quickly lowering the pressure difference to restore smooth flow. This avoids the risk of membrane fouling caused by uneven pressure on the membrane surface due to blockage. In the circulation velocity adjustment stage, increasing the concentrate circulation volume enhances the membrane shear force, promptly flushing away newly attached contaminants and reducing fouling accumulation. If the membrane velocity exceeds the preset range, the concentrate flow rate is maintained by adjusting the high-pressure pump frequency, ensuring the membrane shear force remains within a reasonable range while avoiding excessive energy consumption due to high velocity.

[0044] The first-stage reverse osmosis system can adaptively adjust based on the salinity of the feed water, the quality of the product water, the condition of the pipeline, and the condition of the membrane surface. This ensures that the product water quality is consistently up to standard, while also reasonably controlling energy consumption to meet desalination requirements. At the same time, it reduces the impact of pipeline blockage and membrane fouling on the system, extends the stable operating cycle of the membrane modules and pipelines, and reduces the frequency of downtime maintenance due to parameter imbalances or malfunctions. This makes the operation of the first-stage reverse osmosis system more stable, economical, and reliable.

[0045] Furthermore, the feed water parameters of the reverse osmosis module are adjusted. The specific process is as follows: Based on the current first conductivity, a synergistic desalination index is obtained by combining it with the third conductivity to quantify the synergistic efficiency of the two-stage reverse osmosis membrane, and a desalination comparison is performed. The third conductivity represents the conductivity of the feed water corresponding to the first conductivity after passing through the two-stage reverse osmosis membrane to produce water. The specific process of the desalination comparison is as follows: If the obtained synergistic desalination index is less than the minimum value of the preset synergistic desalination index range, it indicates that the desalination is unqualified. Based on the deviation of the synergistic desalination index, the step size of the increase of the membrane stack electric field strength is obtained to increase the membrane stack voltage until the electric field strength is equal to the preset electric field strength. During the adjustment of the electric field strength, the conductivity in the feed water buffer tank of the first-stage reverse osmosis membrane and the operating temperature of the surface of the two-stage reverse osmosis membrane are monitored in real time. If, after the membrane stack voltage is increased, the re-obtained synergistic desalination index is still greater than the maximum value of the preset first-stage reverse osmosis feed water salinity range, the feed water salinity is adjusted to reduce the feed water salinity corresponding to the first-stage reverse osmosis membrane.

[0046] If the obtained synergistic desalination index is greater than the maximum value of the preset synergistic desalination index range, it indicates that desalination is effective, and the reduction step size of the membrane stack electric field strength is obtained to reduce the membrane stack voltage. Simultaneously, the amount of waste heat reduction corresponding to the reduction of electric field strength is obtained, and the reduction value of the feed water buffer tank flow rate is obtained to reduce the waste heat absorbed by the feed water, so that the operating temperature of the reverse osmosis module surface is within the working range. If the obtained synergistic desalination index is within the preset synergistic desalination index range, the current membrane stack electric field strength is maintained. The feed water salinity adjustment process is as follows: based on the first conductivity deviation, the increase value of the feed water return valve opening is obtained, and the feed water salinity is reduced by increasing the return flow rate of the first-stage reverse osmosis membrane effluent to the feed water end. If the temperature of the first-stage reverse osmosis membrane effluent returning to the feed water end is lower than the temperature of the feed water end side, the amount of waste heat transferred in the electric field stored in the heat-conducting medium is obtained based on the feed water temperature deviation to compensate for the temperature deviation of the mixed feed water and improve the preheating effect.

[0047] In this embodiment, the preset coordinated desalination index range is a closed interval formed by the maximum and minimum values ​​of the coordinated desalination index during the historical influent parameter adjustment process. The coordinated desalination index deviation represents the difference between the obtained coordinated desalination index and the maximum / minimum value of the preset coordinated desalination index range. The step size for increasing / decreasing the membrane stack electric field strength is obtained by training with the historical coordinated desalination index deviation as input and the membrane stack electric field strength as output. The preset electric field strength is a pre-set safe electric field strength threshold.

[0048] The reduction in waste heat due to the decrease in electric field strength is synchronously acquired. The decrease in the inlet buffer tank flow rate is obtained by training a deep neural network regression algorithm, using waste heat as input and inlet buffer tank flow rate as output. Similarly, the inlet recirculation flow rate is similar to that of the inlet buffer tank, so the increase in the inlet recirculation valve opening is also obtained by training the algorithm, using the first conductivity deviation as input and the inlet recirculation valve opening adjustment value as output. Based on the inlet water temperature deviation, the amount of waste heat transferred in the heat transfer medium is obtained by inputting the acquired inlet water temperature deviation into the thermal controller in the two-stage reverse osmosis unit. The controller adjusts the preheating transfer amount according to the pre-set temperature deviation-heat transfer correspondence. The pre-set temperature deviation-heat transfer correspondence is based on the historical thermal controller's correlation inlet water temperature deviation and waste heat transfer amount operating data, and the correspondence is obtained by data fitting. The inlet water temperature deviation represents the difference between the water temperature before and after inlet water recirculation.

[0049] The expression for the synergistic desalination index S is as follows: In the formula, C1 represents the first conductivity, C3 represents the third conductivity, C0 represents the historical average effective value of the first conductivity, and α represents a very small positive number to avoid the denominator being 0 when C3 approaches 0. In practical applications, since C3 will not truly be 0, α can be ignored. The formula, through anti-interference correction terms and purification terms, takes into account both the stability and quality of desalination, and more comprehensively quantifies the synergistic desalination efficiency of the first and second stages of the dual-stage reverse osmosis membrane. In the first part of the formula, the historical average effective value of the first conductivity is used to measure the deviation between the current feed water and the historical normal. The denominator is used to correct for feed water fluctuations, avoiding misjudgment of decreased desalination effect due to the feed water itself becoming more saline, and also ensuring accuracy under stable operating conditions. The second part of the formula reflects the purification capacity of the dual-stage reverse osmosis, and the ratio reflects the purification multiple.

[0050] By dynamically adjusting the feed water parameters of the reverse osmosis components, multi-dimensional optimization of the synergistic desalination efficiency, energy consumption control, and operational stability of the two-stage reverse osmosis membranes is achieved, avoiding system operation problems caused by desalination imbalance, energy waste, or abnormal temperature. Firstly, the synergistic desalination index correlates the salinity of the first-stage reverse osmosis feed water with the quality of the second-stage reverse osmosis permeate, accurately quantifying the overall synergistic desalination effect of the two-stage membranes. This overcomes the limitations of relying solely on parameters of a single membrane stage, making the assessment of desalination effect more closely aligned with the actual operating state of the system and providing a precise basis for subsequent parameter adjustments.

[0051] In optimizing desalination performance, when the synergistic desalination index fails to meet the standard, the electric field strength of the membrane stack is gradually increased to enhance the driving force of ion migration, thereby strengthening the desalination capacity of the two-stage membrane and ensuring that the product water quality approaches the acceptable range. By reducing the salinity of the first-stage reverse osmosis feed water through feed water recirculation, the desalination load on the membrane stack is reduced from the source, preventing the membrane stack from operating at a high load for extended periods due to excessive feed water salinity, effectively reducing losses in the membrane modules caused by excessive desalination. Conversely, when the synergistic desalination index is better than expected, the electric field strength of the membrane stack is appropriately reduced. This reduces unnecessary energy consumption and allows for simultaneous adjustment of the feed water buffer tank flow rate based on waste heat changes, preventing the feed water from absorbing excessive waste heat and causing abnormal membrane surface temperature. This ensures that the reverse osmosis modules always operate within a suitable temperature range, preventing temperature fluctuations from affecting the membrane's permeability and desalination performance.

[0052] Furthermore, the feed water temperature deviation compensation design utilizes the waste heat from the electric field to balance the mixed feed water temperature. This not only improves the feed water preheating effect and prevents a decrease in membrane flux due to low-temperature feed water, but also realizes the resource utilization of waste heat, further optimizing the system's energy consumption structure. This allows the reverse osmosis modules to dynamically adapt the electric field strength, feed water salinity, and temperature according to the desalination effect. This ensures stable compliance of product water quality while rationally controlling energy consumption to meet desalination requirements. Simultaneously, it reduces the adverse effects of temperature, salinity, and other factors on the membrane modules, extending membrane lifespan and improving the overall economic efficiency and reliability of the reverse osmosis system.

[0053] The equipment for a reverse osmosis pure water production method based on synergistic purification of two-stage membrane modules provided in this invention includes: a preliminary filter device, a precision filter device, a freshwater conditioning device, and a two-stage reverse osmosis device; the preliminary filter device includes a preliminary filter for preliminary filtration of raw water and a flow meter for detecting flow rate and velocity; the precision filter device includes a precision filter for tight filtration of the water after preliminary filtration, a flow sensor for detecting flow rate and velocity, and a turbidity sensor for detecting the content of solid particles in the water; the freshwater conditioning device includes a flow sensor for detecting the flow rate at the inlet and outlet of the freshwater chamber, a voltage sensor for detecting the voltage value of electrolytic conditioning in the freshwater chamber, a pH sensor for detecting the pH value before and after freshwater conditioning, and a conductivity sensor for detecting the salinity of the water in the buffer tank; the two-stage reverse osmosis device includes a flow sensor for detecting the flow rate and velocity corresponding to the first-stage and second-stage reverse osmosis membranes, a pressure sensor for detecting the deviation between the water pressure and membrane flux pressure of the two-stage reverse osmosis membranes, and a conductivity sensor for detecting the conductivity of the feed water and product water of the two-stage reverse osmosis membranes.

[0054] In this embodiment, raw water flows sequentially through a preliminary filter, a precision filter, a freshwater conditioning unit, and a two-stage reverse osmosis unit. In the preliminary filter, the raw water undergoes initial filtration, with a flow meter monitoring the flow rate and velocity during filtration. The water then flows to the precision filter, where it undergoes fine filtration. Flow sensors and turbidity sensors monitor the flow rate, velocity, and solid particle content in the water, ensuring filtration accuracy. Next, the water enters the freshwater conditioning unit, where a flow sensor monitors the inlet and outlet flow rates of the freshwater chamber, a voltage sensor detects the electrolysis conditioning voltage, a pH sensor detects the pH before and after conditioning, and a conductivity sensor detects the salinity of the water in the buffer tank, thereby adjusting water quality parameters. Finally, the water enters the two-stage reverse osmosis unit, where a flow sensor monitors the flow rate and velocity of the first and second stage reverse osmosis membranes, a pressure sensor monitors the water pressure and membrane flux pressure deviation, and a conductivity sensor monitors the conductivity of the feed water and product water, achieving synergistic purification through the two-stage membranes. All devices are connected in series via pipelines, and sensors monitor parameters in real time, providing a basis for the control of each stage and ensuring the continuity of pure water production and the stability of water quality.

[0055] The above embodiments can be implemented, in whole or in part, by software, hardware (such as circuits), firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, all or part of the flow or function according to the embodiments of the present invention is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. Computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., infrared, wireless, microwave, etc.) means. A computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more sets of available media. Available media can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., DVDs), or semiconductor media. Semiconductor media can be solid-state drives.

[0056] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0057] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0058] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0059] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0060] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the devices, apparatuses, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0061] In the embodiments provided by this invention, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0062] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0063] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0064] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0065] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A reverse osmosis pure water production method based on synergistic purification of a two-stage membrane module, characterized in that, Includes the following steps: Step 1: In the water quality monitoring stage after pretreatment, the desalination process of the reverse osmosis module is initially optimized based on the acquired ion migration status data to reduce the scaling rate on the reverse osmosis membrane surface. The initial feed water optimization includes ion membrane switching and cleaning status control. The reverse osmosis module includes a freshwater chamber containing an ion exchange membrane, a primary reverse osmosis membrane, and a secondary reverse osmosis membrane. Step 2: Based on the salinity of the feed water at the inlet of the first-stage reverse osmosis membrane after preliminary feed water optimization, pressure-flow rate coordinated control is implemented for the pressure fine desalination process of the first-stage reverse osmosis membrane, while the circulation flow rate is adjusted to reduce the deposition of residual pollutants on the membrane surface. Step 3: Based on the conductivity at the designated location in the feed water buffer tank of the first-stage reverse osmosis membrane, and combined with the feedback status of the permeate water quality of the second-stage reverse osmosis membrane, adjust the feed water parameters of the reverse osmosis module to reduce concentration polarization and membrane fouling caused by the feed water flow rate at the feed water inlet of the first-stage reverse osmosis membrane. The feed water parameters include electric field strength and feed water salinity. The preliminary feed water optimization of the desalination process of the reverse osmosis module is as follows: Preliminary influent water classification is based on the initial pH value in the freshwater chamber, specifically: The first type involves monitoring the anion migration status in the freshwater chamber if the initial pH value in the freshwater chamber is greater than the maximum value of the preset inlet water range. At the same time, a cation exchange membrane switching command is sent to prompt the preset personnel to check the current ion exchange membrane and reduce the pH value of the inlet water in the freshwater chamber. If the current freshwater chamber is in a cation migration state, then based on the current cation migration rate, the increase in electric field strength is obtained to enhance the cation migration efficiency; The second type indicates that if the initial pH value in the freshwater chamber is within the preset feed water range, it means that the working state of the first-stage reverse osmosis membrane is qualified and the current pH value is maintained. The third type involves monitoring the cation migration status in the freshwater chamber if the initial pH value is less than the minimum value of the preset inlet water range, and simultaneously sending an anion exchange membrane switching command to prompt the preset personnel to check the current ion exchange membrane and increase the pH value of the inlet water in the freshwater chamber. If the current freshwater chamber is in anion migration state, then based on the current anion migration rate, the increase in voltage across the ion exchange membrane is obtained to enhance the driving force of the electric field on the ions. After monitoring the ion migration status in the freshwater chamber, the pH value at the freshwater chamber outlet was monitored. The pH monitoring of the freshwater outlet is specifically as follows: If the pH value at the outlet of the freshwater chamber is greater than the maximum value of the preset inlet range, the pH value deviation at the outlet is input into the RO optimal-electrolysis voltage mapping relationship to obtain the increase in electrolysis voltage in the freshwater chamber, so as to increase the migration rate of anions to the acid chamber. The pH value deviation at the outlet represents the difference between the obtained pH value at the outlet of the freshwater chamber and the maximum value of the preset inlet range. If the pH value at the outlet of the freshwater chamber is less than the minimum value of the preset inlet range, the pH value deviation at the outlet is input into the RO optimal-electrolysis voltage mapping relationship to obtain the reduction value of the electrolysis voltage in the freshwater chamber, so as to reduce the migration rate of cations to the alkaline chamber. The pH value deviation at the outlet represents the difference between the obtained pH value at the outlet of the freshwater chamber and the minimum value of the preset inlet range. If the pH value at the freshwater chamber outlet is within the preset inlet range, the current electrolysis voltage is maintained, and the freshwater inlet flow rate is matched with the electrolysis voltage, specifically: If the current electrolysis voltage increases relative to the set electrolysis voltage, the reduction value of the operating speed of the inlet variable frequency pump is obtained according to the preset voltage-flow matching curve, and the flow rate is reduced to extend the mechanical residence time of the ion water; If the current electrolysis voltage decreases relative to the set electrolysis voltage, the increase in the operating speed of the variable frequency pump at the inlet end is obtained according to the preset voltage-flow matching curve, and the hydraulic residence time is reduced by increasing the flow rate. The voltage-flow matching curve is used to visualize the mapping relationship between the corresponding electrolysis voltage and the influent flow rate during the electrolysis water treatment process. When the electrolysis voltage is adjusted, the adjustment value of the influent flow rate is obtained synchronously through this curve.

2. The reverse osmosis pure water production method based on synergistic purification of a two-stage membrane module as described in claim 1, characterized in that, The cleaning status control includes cleaning status control of ion exchange membranes for improving electrolysis efficiency and cleaning status control of reverse osmosis membranes for improving reverse osmosis efficiency, specifically: The process for controlling the cleaning status of the ion exchange membrane is as follows: The pH value of the freshwater outlet corresponding to the ion exchange membrane in the cleaning tank is monitored in real time. If the pH value of the freshwater outlet is not within the preset outlet range, the pH value deviation is input into the ion outlet-circulation time mapping relationship to obtain the reduction value of the desalination cycle time, so as to reduce the subsequent scaling efficiency. The reverse osmosis membrane cleaning status control is specifically as follows: Based on the concentration deviation of the cleaning solution after the ion exchange membrane cleaning status is controlled, the circulation flow rate adjustment value of the dual-stage reverse osmosis membrane is obtained to reduce the probability of scaling on the surface of the dual-stage reverse osmosis membrane. The dual-stage reverse osmosis membrane includes a primary reverse osmosis membrane and a secondary reverse osmosis membrane. The concentration deviation of the cleaning solution is used to reflect the degree of cleaning corresponding to the dual-stage reverse osmosis membrane. If the concentration of the cleaning solution after the reverse osmosis membrane cleaning status control is greater than the preset cleaning solution concentration, a reflux command is sent to recycle the cleaning solution; otherwise, a cleaning solution waste command is sent to discharge the cleaning solution into wastewater treatment. The cleaning solution includes a cleaning acid solution and a cleaning alkali solution.

3. The reverse osmosis pure water production method based on synergistic purification of a two-stage membrane module as described in claim 1, characterized in that, The pressure-flow rate coordinated control of the pressure fine desalination process of the first-stage reverse osmosis membrane is as follows: Based on the salt content in the feed water buffer tank of the first-stage reverse osmosis membrane, the first conductivity is obtained and compared with the preset reverse osmosis conductivity range: If the obtained first conductivity is greater than the maximum value of the preset reverse osmosis conductivity range, the adjustment value of the pressure increase step size is obtained based on the deviation of the first conductivity, so as to increase the water pressure increase of the first-stage reverse osmosis membrane until the first conductivity is within the preset reverse osmosis conductivity range. During the water pressure adjustment process, the conductivity of the permeate after passing through the first-stage reverse osmosis membrane is monitored in real time to obtain the second conductivity. If the second conductivity is greater than the preset second conductivity of the first-stage reverse osmosis membrane when the water pressure is increased to the preset permeate pressure, the water pressure adjustment is suspended and a water conductivity warning command is sent to investigate desalination failure. If the obtained first conductivity is less than the minimum value of the preset reverse osmosis conductivity range, the pressure reduction step size is adjusted based on the deviation of the first conductivity to reduce the water pressure reduction of the first-stage reverse osmosis membrane. If the second conductivity is still less than the preset second conductivity of the first-stage reverse osmosis membrane after the water pressure is reduced, it indicates that the pressure reduction is effective. Otherwise, the high-pressure pump is prompted to return to the water pressure corresponding to the water pressure before the water pressure was reduced. The second conductivity represents the conductivity of the product water obtained by the feed water corresponding to the first conductivity passing through the first-stage reverse osmosis membrane.

4. The reverse osmosis pure water production method based on synergistic purification of a two-stage membrane module as described in claim 3, characterized in that, The comparison with the preset reverse osmosis conductivity range also includes: If the obtained first conductivity is within the preset reverse osmosis conductivity range, it indicates that the salt content of the feed water to the first-stage reverse osmosis membrane is stable and the current water pressure on the first-stage reverse osmosis membrane is maintained. During the adjustment of water pressure, the osmotic pressure difference between the inlet and the outlet is monitored in real time. If the membrane flux pressure deviation is greater than the preset membrane flux pressure deviation, and the water pressure increases to the preset permeate pressure, it indicates that the pipeline is blocked. Based on the currently obtained membrane flux pressure deviation, the increase in permeate circulation velocity is obtained. By increasing the pipeline flushing rate, the membrane flux pressure deviation and osmotic pressure difference are reduced. The membrane flux pressure deviation represents the difference between the obtained pressure at the inlet and the pressure at the permeate outlet. After the permeate circulation flow rate increases, the membrane flux pressure deviation is re-acquired. When the membrane flux pressure deviation is less than the preset membrane flux pressure deviation, the current permeate circulation flow rate is maintained.

5. The reverse osmosis pure water production method based on synergistic purification of a two-stage membrane module as described in claim 4, characterized in that, The specific process for adjusting the circulation flow rate is as follows: Based on the obtained membrane surface water flow velocity, it is input into the membrane surface flow velocity-concentrate recirculation mapping relationship to obtain the concentrate recirculation rate adjustment value, so as to increase the concentrate circulation volume, and the membrane surface water flow velocity is re-obtained. The membrane surface water flow velocity and the pressure difference between the inside and outside of the membrane represent the membrane surface water flow velocity and the pressure difference between the inside and outside of the membrane corresponding to the first stage reverse osmosis membrane. If the re-acquired membrane surface water flow velocity is greater than the preset membrane surface water flow velocity, then based on the currently acquired membrane inside and outside pressure difference, the adjustment value of the high-pressure pump frequency is obtained to maintain the concentrate flow rate and increase the membrane surface shear force. The concentrate refers to the water flow that has not passed through the first-stage reverse osmosis membrane, and the membrane inside and outside pressure difference is the difference between the pressure inside the first-stage reverse osmosis membrane and the pressure outside the first-stage reverse osmosis membrane.

6. The reverse osmosis pure water production method based on synergistic purification of a two-stage membrane module as described in claim 3, characterized in that, The specific process for adjusting the feed water parameters of the reverse osmosis module is as follows: Based on the current first conductivity, a synergistic desalination index is obtained by combining it with the third conductivity to quantify the synergistic efficiency of the two-stage reverse osmosis membrane, and a desalination comparison is performed. The third conductivity represents the conductivity of the feed water corresponding to the first conductivity after passing through the two-stage reverse osmosis membrane to produce water. The specific process of the desalination comparison is as follows: If the obtained synergistic desalination index is less than the minimum value of the preset synergistic desalination index range, it indicates that the desalination is unqualified. Based on the deviation of the synergistic desalination index, the step size of the increase of the electric field strength of the membrane stack is obtained to increase the membrane stack voltage until the electric field strength is equal to the preset electric field strength. During the adjustment of the electric field strength, the conductivity in the feed water buffer tank of the first-stage reverse osmosis membrane and the operating temperature of the surface of the two-stage reverse osmosis membrane are monitored in real time. If the re-obtained synergistic desalination index is still less than the minimum value of the preset first-stage reverse osmosis feed water salinity range after the membrane stack voltage is increased, the feed water salinity is adjusted to reduce the feed water salinity corresponding to the first-stage reverse osmosis membrane.

7. The reverse osmosis pure water production method based on synergistic purification of a two-stage membrane module as described in claim 6, characterized in that, The desalination comparison also includes: If the obtained synergistic desalination index is greater than the maximum value of the preset synergistic desalination index range, it indicates that the desalination is effective. The reduction step size of the membrane stack electric field strength is obtained to reduce the membrane stack voltage. At the same time, the amount of waste heat reduction corresponding to the reduction of electric field strength is obtained, and the reduction value of the feed water buffer tank flow rate is obtained to reduce the waste heat absorbed by the feed water, so that the operating temperature of the reverse osmosis module surface is within the working range. If the obtained synergistic desalination index is within the preset synergistic desalination index range, then the current membrane stack electric field strength is maintained. The specific process for adjusting the salinity of the feed water is as follows: Based on the first conductivity deviation, the increase value of the opening of the feed water return valve is obtained, and the feed water salinity is reduced by increasing the return flow rate of the first-stage reverse osmosis membrane outlet to the feed water end. If the temperature of the first-stage reverse osmosis membrane outlet water returning from the inlet is lower than the temperature at the inlet side, the amount of heat transferred from the electric field stored in the heat-conducting medium is obtained based on the inlet water temperature deviation, in order to compensate for the temperature deviation of the mixed inlet water and improve the preheating effect.

Images