A low-pressure high-multiple-concentration method and system for high-salinity wastewater

Abstract

The application relates to a high-salt wastewater low-pressure high-multiple concentration method and system, and relates to the technical field of wastewater concentration. The application has the effect of expanding the water quality adaptation range of high-salt wastewater concentration.

Description

Technical Field

[0001] This application relates to the technical field of wastewater concentration, and in particular to a method and system for low-pressure high-concentration of high-salt wastewater. Background Technology

[0002] Low-pressure high-concentration of saline wastewater refers to increasing the salt concentration in wastewater by several times or even dozens of times under relatively low pressure, thereby greatly reducing the volume of waste liquid that needs to enter the high-energy-consuming evaporator and significantly reducing the overall treatment cost.

[0003] In related technologies, Chinese patent document CN116924521A discloses a high-concentration wastewater concentration system and concentration method, including an auxiliary reverse osmosis concentration treatment step. The wastewater to be treated with a sodium chloride concentration greater than or equal to 70000 mg / L is pressurized to 60 to 70 bar, and then enters the high-pressure side of the first-stage auxiliary reverse osmosis concentration device. Then it enters the second-stage auxiliary reverse osmosis concentration device for a second-stage auxiliary reverse osmosis concentration treatment. The system also includes a reverse osmosis concentration treatment step, in which the extract after the auxiliary reverse osmosis concentration treatment is subjected to a first reverse osmosis treatment and a second reverse osmosis treatment to obtain the final product water.

[0004] The aforementioned technologies are applicable to a limited range of wastewater types, specifically high-concentration sodium chloride wastewater. When treating multi-component wastewater containing high calcium and high silicon, the reverse osmosis membrane surface rapidly crystallizes, causing scaling and blockage. This results in a narrow range of water quality adaptability for high-salt wastewater concentration, leaving room for improvement. Summary of the Invention

[0005] In order to expand the range of water quality adaptability for high-salinity wastewater concentration, this application provides a method and system for low-pressure high-concentration of high-salinity wastewater.

[0006] In the first aspect, this application provides a method for low-pressure, high-concentration of high-salinity wastewater, employing the following technical solution: A method for low-pressure, high-concentration of high-salinity wastewater includes: Obtain the water quality testing parameters of the wastewater to be treated; Based on water quality testing parameters, the wastewater to be treated is pretreated in different categories to achieve targeted pollution removal, and a pretreatment completion trigger signal is obtained; Based on the pretreatment completion trigger signal, the pretreated wastewater is subjected to membrane concentration treatment to achieve water-salt separation, and the membrane concentration completion trigger signal is obtained. Salt is recovered from the product water after water-salt separation based on the trigger signal of membrane concentration completion, so as to realize the recycling of water resources.

[0007] Optionally, the steps of performing differentiated pretreatment of the wastewater to be treated based on water quality testing parameters to achieve targeted pollution removal include: Determine whether the water quality testing parameters meet the preset requirements for calcium- and silicon-rich water quality parameters; If it does not meet the requirements, the wastewater to be treated shall be filtered. If the conditions are met, the wastewater to be treated will be pretreated according to the water quality testing parameters to achieve targeted pollution removal, and the pretreated wastewater will be filtered. Obtain the filtered water quality parameters; When the filtered water quality parameters do not meet the preset water quality standards, the wastewater to be treated is re-treated by different grades until the filtered water quality parameters meet the water quality standards.

[0008] Optionally, the steps of pretreating the wastewater to be treated based on water quality testing parameters to achieve targeted pollution removal include: Determine if the water quality test parameters are within the preset range of single silica water quality parameters, preset range of single calcium water quality parameters, or preset range of mixed water quality parameters. If the water quality parameters are within the range of single silicon, the preset silicon adsorption column is controlled to adsorb silicon into the wastewater to be treated in order to remove silicon elements in a targeted manner. If the water quality parameters are within the range of single calcium, then a pre-set composite scale inhibitor and carbon dioxide are added to the wastewater to be treated to target and remove calcium. If the water quality parameters are within the range of mixed parameters, the wastewater to be treated should be pretreated by mixing to target the removal of calcium and silicon.

[0009] Optionally, the step of adding a pre-set composite scale inhibitor and carbon dioxide to the wastewater to be treated to target the removal of calcium includes: The wastewater calcium hardness, wastewater influent flow rate, wastewater hydrogen ion concentration, and wastewater total alkalinity are determined based on water quality testing parameters. The scale inhibitor dosage is calculated based on the pre-set scale inhibitor model, which calculates the calcium hardness of the wastewater and the influent flow rate. The target dissolved inorganic carbon is found in the preset calcium hardness-dissolved inorganic carbon correspondence based on the calcium hardness of the wastewater. Based on a pre-defined dissolved inorganic carbon model, the target dissolved inorganic carbon, wastewater hydrogen ion concentration, and wastewater total alkalinity are calculated to generate a dissolved inorganic carbon deviation. The dissolved inorganic carbon deviation and wastewater influent flow rate are calculated based on a pre-set carbon dioxide model to generate the carbon dioxide dosage. Based on the dosage of scale inhibitor and carbon dioxide, a composite scale inhibitor and carbon dioxide are added to the wastewater to be treated to target the removal of calcium. The expression for the scale inhibitor model is: ; In the formula, This refers to the dosage of scale inhibitor. As a preset safety redundancy factor, For the calcium hardness of wastewater, This refers to the wastewater influent flow rate. This is the preset efficiency coefficient for the complexation reaction of the scale inhibitor. This is the preset effective concentration of the scale inhibitor; The expression for the dissolved inorganic carbon model is: ; In the formula, To dissolve the deviation of inorganic carbon, To dissolve inorganic carbon, The total alkalinity of the wastewater. This refers to the hydrogen ion concentration in the wastewater. This is the preset first-order dissociation constant of carbonic acid. This is the preset second-order dissociation constant of carbonic acid; The expression for the carbon dioxide model is: ; In the formula, This refers to the amount of carbon dioxide emitted. The preset carbon dioxide dissolution utilization coefficient, This refers to the wastewater influent flow rate. To address the deviation in dissolving inorganic carbon.

[0010] Optionally, the step of performing membrane concentration on the pretreated wastewater to achieve water-salt separation based on the pretreatment completion trigger signal includes: Based on the pretreatment completion trigger signal, the wastewater to be treated is pressurized and passed through a preset reverse osmosis membrane module to produce freshwater and wastewater; the freshwater is used for salt recovery, and the wastewater is used for pressurization. Obtain the real-time operating flux of the reverse osmosis membrane module; Determine whether the real-time operating throughput meets the preset throughput warning threshold requirements; If the conditions are met, the wastewater to be treated will be pressurized and passed through a pre-set reverse osmosis membrane module to produce fresh water and wastewater. If it does not meet the requirements, the reverse osmosis membrane module will be backwashed until the real-time operating flux meets the flux warning threshold.

[0011] Optionally, the step of pressurizing the wastewater to be treated and passing it through a preset reverse osmosis membrane module to produce freshwater and wastewater based on a pretreatment completion trigger signal includes: Based on the pretreatment completion trigger signal, the preset pressure exchanger is controlled to transmit the wastewater pressure to the wastewater to be treated to produce pressurized wastewater and depressurized wastewater; the depressurized wastewater is used to backwash the reverse osmosis membrane module; Obtain the pressure transmission pressure of the pressurized wastewater to be treated; The difference between the preset target pressure and the boost pressure is calculated to generate additional pressure. The wastewater to be treated is pressurized by adding extra pressure and passed through the reverse osmosis membrane module to produce fresh water and wastewater.

[0012] Optionally, the steps of recovering salt from the product water after water-salt separation based on the membrane concentration completion trigger signal to achieve water resource recycling include: The type of compliant permeate is determined based on the trigger signal indicating completion of membrane concentration. Salt is recovered from the water after water-salt separation to produce final product water, depending on the type of product water that meets the standards. Obtain the final product water quality parameters; Determine whether the product water quality parameters meet the preset requirements for compliant product water quality parameters; If the conditions are met, the final produced water will be sent to the pre-designed reuse network to achieve water resource recycling. If it does not meet the requirements, the final product water will be re-concentrated using a membrane.

[0013] Optionally, the steps of recovering salt from the water-salt separation product water to produce final product water, depending on the type of product water that meets the standards, include: Determine whether the qualified product water type meets the preset requirements for the multi-salt mixed product water type; If not, the product water after water-salt separation is directly evaporated and crystallized to produce crystalline salt and final product water; If the conditions are met, the preset nanofiltration desalination module will be controlled to separate salts in the product water after water-salt separation, so as to produce water with a single salt content. Evaporation and crystallization are performed on a single salt-rich product water to produce crystalline salt and final product water.

[0014] Secondly, this application provides a low-pressure, high-concentration system for high-salinity wastewater, employing the following technical solution: A low-pressure, high-concentration system for high-salinity wastewater includes: The acquisition module is used to acquire water quality testing parameters, pretreatment completion trigger signal, and membrane concentration completion trigger signal; A memory for storing a program for a low-pressure, high-concentration method for high-salt wastewater as described in any of the preceding claims; The processor and the program in the memory can be loaded and executed by the processor to implement a low-pressure, high-concentration method for high-salt wastewater as described in any of the above.

[0015] In summary, this application includes at least one of the following beneficial technical effects: 1. By detecting the water quality parameters of the wastewater to be treated, the wastewater to be treated is pretreated and targeted to remove pollutants according to the water quality parameters. For wastewater with high calcium, high silicon or mixed salt, the corresponding hardness removal, silicon removal or composite scale inhibition treatment is automatically matched and executed, overcoming the limitation of existing special concentration technology that is applicable to a single water quality, thereby expanding the water quality adaptability range of high salinity wastewater concentration. 2. By monitoring membrane flux in real time, and using depressurized wastewater to backwash the reverse osmosis membrane module when the membrane flux drops to the flux warning threshold, the flux of the reverse osmosis membrane module can be effectively restored, reducing the need for chemical cleaning and significantly reducing membrane fouling rate and maintenance costs. 3. By directly using the pressure of the wastewater to be treated through a pressure exchanger, the pressure of the pressurized wastewater is increased. Then, the pressure of the pressurization transmission is detected, and the difference between the target pressure and the pressure of the pressurization transmission is calculated to obtain the additional pressure. Based on the additional pressure, the pressurized wastewater to be treated is pressurized again, which greatly reduces the energy load of pressurization and realizes energy recovery and utilization. Attached Figure Description

[0016] Figure 1 This is a flowchart of a low-pressure, high-concentration method for high-salt wastewater according to an embodiment of this application.

[0017] Figure 2 This is a flowchart of the steps in this application embodiment to perform pretreatment of wastewater according to water quality testing parameters to achieve targeted pollution removal.

[0018] Figure 3 This is a flowchart of the steps in this application embodiment to pretreat the wastewater to be treated according to water quality testing parameters to achieve targeted pollution removal.

[0019] Figure 4 This is a flowchart of the steps in this application embodiment of adding a preset composite scale inhibitor and carbon dioxide to the wastewater to be treated in order to target the removal of calcium.

[0020] Figure 5 This is a flowchart of the steps in this application embodiment to perform membrane concentration treatment on the pretreated wastewater to achieve water-salt separation based on the pretreatment completion trigger signal.

[0021] Figure 6 This is a flowchart of the steps in this application embodiment of the process of pressurizing the wastewater to be treated and passing it through a preset reverse osmosis membrane module to produce fresh water and wastewater based on a pretreatment completion trigger signal.

[0022] Figure 7 This is a flowchart of the steps in this application embodiment to recover salt from the product water after water-salt separation based on the membrane concentration completion trigger signal to achieve water resource recycling.

[0023] Figure 8This is a flowchart of the steps in this application embodiment to recover salt from the water after water-salt separation to produce the final water, based on the type of qualified water produced. Detailed Implementation

[0024] To make the purpose, technical solution, and advantages of this application clearer, the following description is provided in conjunction with the appendix. Figures 1 to 8 The present application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the application.

[0025] Reference Figure 1 This application discloses a method for high-salinity wastewater concentration under low pressure, comprising the following steps: Step S100: Obtain the water quality testing parameters of the wastewater to be treated.

[0026] In the process of low-pressure high-concentration of high-salinity wastewater, existing technologies can only treat wastewater containing sodium chloride. For water containing salts such as calcium and silicon, they cannot accurately remove contaminants, which can easily cause scale buildup on the membrane surface and lead to blockage. Therefore, to reduce the risk of membrane scaling, it is necessary to first identify the specific salts contained in the wastewater to be treated, such as calcium and silicon, and then perform targeted decontamination to reduce the risk of scaling and expand the range of water quality suitable for high-salinity wastewater concentration. Therefore, the water quality parameters of the wastewater to be treated are tested to serve as the data source for targeted decontamination.

[0027] The water quality testing parameters are a set of parameters reflecting the salt content of the wastewater crystallizing on the membrane surface, including total dissolved solids (TDS), calcium hardness, silicon content, turbidity, hydrogen ion concentration, and total alkalinity. In one embodiment, the water quality testing parameters are obtained by real-time sampling and electrochemical analysis of the wastewater by a multi-parameter water quality sensor installed on the inlet pipe of the wastewater, and the test results are sent to the treatment terminal. In another embodiment, the parameters can also be obtained by offline sampling in the laboratory and inputting the data into the treatment terminal by the operator, as long as the data requirements are met.

[0028] Step S101: Perform pretreatment of the wastewater to be treated according to the water quality detection parameters to achieve targeted pollution removal, and obtain the pretreatment completion trigger signal.

[0029] After determining the water quality testing parameters, pretreatment can be performed based on the type and content of salts corresponding to these parameters. This allows for targeted removal of high-concentration salts. Specific methods are detailed below. Figure 2This process avoids the rapid crystallization of high-concentration salts on the membrane surface, which could lead to blockage, during subsequent membrane concentration treatment of the wastewater. It also detects the pretreatment completion trigger signal to ensure that the salt concentration in the wastewater has decreased to below the threshold, preventing substandard wastewater from entering the membrane concentration treatment stage and increasing the risk of membrane scaling.

[0030] The pretreatment completion trigger signal is the signal that the pretreatment of the wastewater to be treated has been completed. During the pretreatment process, the pretreated wastewater enters the intermediate water tank, where multi-parameter water quality sensors sample and electrochemically analyze the wastewater in real time. When the wastewater meets the standards (turbidity less than or equal to 1 NTU, calcium hardness less than or equal to 500 mg / L, and silicon content less than or equal to 30 mg / L), it indicates that the salt content that may cause membrane scaling and clogging is extremely low. The wastewater after targeted decontamination can then be concentrated using membrane treatment. Therefore, the treatment terminal activates the pretreatment completion trigger signal. If the standards are not met, the wastewater is returned from the intermediate water tank to the pretreatment step for re-pretreatment. The pretreatment completion trigger signal serves as a prerequisite for pressurization during membrane concentration treatment, completely blocking the risk of substandard hard water entering the reverse osmosis membrane module, thereby fundamentally avoiding irreversible scaling and fouling on the membrane surface.

[0031] Step S102: Based on the pretreatment completion trigger signal, perform membrane concentration treatment on the pretreated wastewater to achieve water-salt separation, and obtain the membrane concentration completion trigger signal.

[0032] In this process, after receiving the pretreatment completion trigger signal, the processing terminal responds by performing membrane concentration treatment on the pretreated wastewater in the intermediate water tank. This separates the wastewater into low-salinity freshwater (product water) and high-salinity concentrated water (wastewater), achieving water-salt separation. The specific method is described in [reference needed]. Figure 5 The process involves following these steps and detecting the trigger signal for membrane concentration completion to confirm that the water-salt separation process is complete and that salt recovery and product water reuse can begin.

[0033] The membrane concentration completion trigger signal is the trigger signal for completing the membrane concentration treatment of the wastewater to be treated. During the membrane concentration triggering process of the wastewater to be treated, when the water quality multi-parameter sensor detects that the flow rate of the permeate and the concentration of the wastewater have reached the set separation target threshold, the treatment terminal activates the membrane concentration completion trigger signal.

[0034] Step S103: Based on the membrane concentration completion trigger signal, salt is recovered from the product water after water-salt separation to achieve water resource recycling.

[0035] In this process, after receiving the membrane concentration completion trigger signal, the processing terminal responds by recovering salt from the permeate (freshwater) produced by the membrane concentration treatment to obtain solid salt products. The recycled water, after passing quality testing, is then returned to the pipeline network, thus achieving water resource recycling. Specific methods are detailed below. Figure 7 The steps.

[0036] Reference Figure 2 The steps for targeted pollution removal by pretreating wastewater according to water quality testing parameters include: Step S200: Determine whether the water quality testing parameters meet the preset requirements for calcium- and silicon-rich water quality parameters.

[0037] The calcium- and silicon-rich water quality parameters are the minimum calcium hardness and minimum silicon content required for targeted decontamination. In this embodiment, the minimum calcium hardness is 1500 mg / L and the minimum silicon content is 100 mg / L. These parameters are set based on the crystallization kinetics of the reverse osmosis membrane surface: when the calcium hardness exceeds 1500 mg / L, under membrane concentration pressure of 55 to 65 bar, the supersaturation of calcium carbonate easily exceeds the critical precipitation point, causing rapid scaling on the membrane surface. Similarly, when the silicon content exceeds 100 mg / L, the polymerization conversion rate of colloidal and dissolved silicon increases sharply, easily forming difficult-to-clean silicon scale. It should be understood that although this embodiment lists specific thresholds of 1500 mg / L and 100 mg / L, in other embodiments, these thresholds can be dynamically adjusted according to the membrane module's tolerance and the influent water temperature, as long as the function of blocking the risk of irreversible scaling on the membrane surface is met. The requirement for the calcium- and silicon-rich water quality parameters is that the calcium hardness and silicon content in the water quality test parameters are not lower than the corresponding calcium hardness and silicon content for the calcium- and silicon-rich water quality parameters.

[0038] By using a processing terminal to determine whether the calcium hardness and silicon content in the water quality testing parameters are not lower than the calcium hardness and silicon content corresponding to water rich in calcium and silicon, it can be determined whether the wastewater to be treated is rich in calcium and silicon and whether targeted decontamination is required.

[0039] Step S201: If it does not meet the requirements, then filter the wastewater to be treated.

[0040] If the treatment terminal determines that the calcium hardness and silicon content in the water quality test parameters are lower than the calcium hardness and silicon content corresponding to the parameters of water rich in calcium and silicon, it indicates that the risk of scaling on the membrane surface is low when the wastewater to be treated is concentrated. In this case, there is no need to perform targeted decontamination. It is only necessary to turn on the quartz sand filter to perform conventional filtration of the wastewater to be treated, thereby filtering out suspended solids and large colloids in the wastewater to be treated, so as to ensure that the effluent turbidity meets the influent requirements of membrane concentration treatment.

[0041] Step S202: If the conditions are met, the wastewater to be treated is pretreated according to the water quality testing parameters to achieve targeted pollution removal, and the pretreated wastewater to be treated is filtered.

[0042] If the treatment terminal determines that the calcium hardness and silicon content in the water quality testing parameters are not lower than the calcium hardness and silicon content corresponding to water rich in calcium and silicon, it indicates that the risk of membrane scaling caused by calcium or silicon in the wastewater to be treated is high. Therefore, pretreatment of the wastewater to be treated should be carried out according to the specific calcium hardness and silicon content in the water quality testing parameters to accurately remove calcium and silicon from the wastewater to be treated and reduce the risk of membrane scaling. The specific method is as follows: Figure 3 The process involves using a quartz sand filter to filter the pretreated wastewater, thereby removing the microcrystals and flocs generated during the pretreatment process.

[0043] Step S203: Obtain the filtered water quality parameters.

[0044] After filtering the wastewater, the next step is membrane concentration. However, to perform membrane concentration, it is necessary to ensure that the water quality of the wastewater meets the standards. Therefore, the water quality parameters of the filtered water are tested to determine the current water quality of the wastewater and to ensure that membrane concentration is not performed if the water quality does not meet the standards.

[0045] The filtered water quality parameters are the water quality parameters of the wastewater to be treated after filtration, including turbidity, calcium hardness and silicon content. After filtration, the wastewater to be treated enters the intermediate water tank. The multi-parameter water quality sensor detects the wastewater to be treated and sends the results to the treatment terminal.

[0046] Step S204: When the filtered water quality parameters do not meet the preset water quality standards, the wastewater to be treated is subjected to separate pretreatment until the filtered water quality parameters meet the water quality standards.

[0047] The water quality compliance parameters are those indicating that the wastewater to be treated can undergo membrane concentration treatment. Examples include turbidity of 1 NTU, calcium hardness of 500 mg / L, and silicon content of 30 mg / L. The requirement for these water quality compliance parameters is that they do not exceed the corresponding turbidity, calcium hardness, and silicon content.

[0048] When the turbidity, calcium hardness, and silicon content of the filtered water exceed the water quality standards at the treatment terminal, it indicates that the water quality of the filtered wastewater is still substandard. The single pretreatment process failed to reduce the hardness of the wastewater below the safety line. Therefore, the wastewater in the intermediate tank is returned to the pretreatment front end for targeted decontamination. This cycle is repeated until the turbidity, calcium hardness, and silicon content of the effluent do not exceed the water quality standards. This cyclic retreatment mechanism greatly reduces the possibility of residual hard water entering the membrane module.

[0049] Reference Figure 3 The steps for pretreating wastewater to achieve targeted pollution removal based on water quality testing parameters include: Step S300: Determine that the water quality detection parameters are within the preset range of single-silicon water quality parameters, the preset range of single-calcium water quality parameters, or the preset range of mixed water quality parameters.

[0050] The water quality parameters for single-silicon water are defined as those with calcium hardness below 1500 mg / L but silicon content exceeding 100 mg / L. The water quality parameters for single-calcium water are defined as those with silicon content below 100 mg / L but calcium hardness exceeding 1500 mg / L. The water quality parameters for mixed water are defined as those with calcium hardness exceeding 1500 mg / L and silicon content exceeding 100 mg / L.

[0051] By processing the terminal to determine whether the calcium hardness and silicon content corresponding to the water quality testing parameters fall within the range of single silicon water quality parameters, single calcium water quality parameters, or mixed water quality parameters, the method for removing silicon and calcium can be determined.

[0052] Step S301: If the water quality parameters are within the range of single silicon, control the preset silicon adsorption column to adsorb silicon into the wastewater to be treated in order to target and remove silicon.

[0053] If the treatment terminal determines that the calcium hardness and silicon content corresponding to the water quality detection parameters are within the range of single silicon water quality parameters, it indicates that the calcium hardness in the wastewater to be treated is low, but the silicon content is high. Therefore, it is necessary to remove the silicon from the wastewater to be treated. The wastewater to be treated is passed into the silicon adsorption column from top to bottom, and the filtration speed is controlled at 6 to 8 m / h. The empty bed contact time is 10 to 15 minutes to ensure that the water and the adsorbent are in full contact and complete the directional adsorption and removal of silicon.

[0054] A silicon adsorption column is a device for adsorbing silicon from wastewater. The column is connected to the inlet pipeline via a valve and is filled with modified activated carbon packing. This packing achieves specific adsorption of silicon by loading aluminum ions. The microscopic mechanism is that the loaded aluminum ions form aluminum hydroxyl complexes in the aqueous solution. These complexes carry a positive charge, while dissolved and colloidal silicon in the water carries a negative charge. The two combine through strong electrostatic attraction and chemical coordination, thus firmly anchoring the silicon to the packing surface. The silicon removal rate can reach over 80%. Compared to the traditional method of adding silicon removal agents, which generates a large amount of sludge, this physical adsorption method eliminates the need for subsequent sludge treatment, significantly reducing solid waste disposal costs. When the soluble silica concentration in the effluent from the silicon adsorption column exceeds 50 mg / L, the column is considered to have broken through, and the system is switched to a backup adsorption column.

[0055] Step S302: If the water quality parameters are within the range of single calcium, then add the preset composite scale inhibitor and carbon dioxide to the wastewater to be treated to target and remove calcium.

[0056] If the treatment terminal determines that the calcium hardness and silicon content corresponding to the water quality testing parameters are within the range of single-calcium water quality parameters, it indicates that the silicon content in the wastewater to be treated is low, but the calcium hardness is high. Therefore, it is necessary to remove the calcium from the wastewater to be treated. This involves starting the calcification reactor and adding a composite scale inhibitor and carbon dioxide to the wastewater to target and remove the calcium. Specific methods are described in [reference needed]. Figure 4 The steps.

[0057] The composite scale inhibitor is composed of polyepoxysuccinic acid (50%-60% by mass), hydroxyethylidene diphosphonic acid (20%-30%), and nano-calcium carbonate (10%-20%). Among them, polyepoxysuccinic acid and hydroxyethylidene diphosphonic acid act as chelating groups, which can undergo a strong complexation reaction with calcium ions in water, encapsulating the calcium ions within the chelating ring and preventing them from combining with carbonate ions and precipitating. When carbon dioxide is introduced, it dissolves in water to form carbonic acid, lowering the local pH value and providing additional carbonate ions. Under the dispersing effect of the scale inhibitor, the chelated calcium ions are precipitated in the form of extremely small calcium carbonate microcrystals and suspended in the water, and are then easily filtered out by the quartz sand filter, rather than forming scale on the membrane surface. It has the functions of chelating calcium and magnesium ions (scale inhibition rate ≥90%) and dispersing silicon particles (silicon removal rate ≥80%). The cost is only 50% of that of traditional "lime-soda ash" softening agents, and there is no need for sedimentation sludge treatment.

[0058] Step S303: If the water quality parameters are within the range of mixed water quality parameters, the wastewater to be treated shall be mixed and pretreated to target the removal of calcium and silicon elements.

[0059] If the treatment terminal determines that the calcium hardness and silicon content corresponding to the water quality testing parameters are within the range of mixed water quality parameters, it indicates that the calcium and silicon in the wastewater to be treated both exceed the standard. Therefore, the calcification reactor and the silicon adsorption column are started at the same time, or a composite scale inhibitor with the functions of removing hardness and dispersing silicon particles is added to the calcification reactor. First, the calcium ions are chelated and precipitated and dispersed into silica gel through the reaction of the agent. Then, the residual silicon is adsorbed through the silicon adsorption column, thereby targeting and removing calcium and silicon elements.

[0060] Reference Figure 4 The steps of adding a pre-set composite scale inhibitor and carbon dioxide to the wastewater to target and remove calcium include: Step S400: Determine the wastewater calcium hardness, wastewater influent flow rate, wastewater hydrogen ion concentration, and wastewater total alkalinity based on the water quality testing parameters.

[0061] Among these metrics, calcium hardness refers to the concentration of calcium ions in the wastewater, reflecting the concentration load of core ions that cause scaling. Higher calcium hardness indicates a greater risk of scaling. Influent flow rate refers to the flow rate of wastewater into the influent pipeline; a higher flow rate indicates a larger volume of water requiring treatment. Hydrogen ion concentration refers to the concentration of hydrogen ions in the wastewater, calculated from its pH value. Hydrogen ion concentration determines the dissociation equilibrium of carbonic acid in water. Total alkalinity refers to the total alkalinity of the wastewater; lower total alkalinity indicates a weaker ability to neutralize acids.

[0062] Step S401: Calculate the calcium hardness of the wastewater and the influent flow rate based on the preset scale inhibitor model to generate the scale inhibitor dosage.

[0063] The scale inhibitor model is used to calculate the required amount of composite scale inhibitor, and its specific expression is as follows: .

[0064] In the formula, This refers to the dosage of scale inhibitor. As a preset safety redundancy factor, For the calcium hardness of wastewater, This refers to the wastewater influent flow rate. This is the preset efficiency coefficient for the complexation reaction of the scale inhibitor. This is the preset effective concentration of the scale inhibitor.

[0065] This model is based on the calcium hardness load matching method. It accurately matches the dosage of scale inhibitor according to the total amount of calcium ions, combined with the agent complexation efficiency and safety redundancy coefficient. The product of calcium hardness and flow rate reflects the total amount of calcium ions. The larger the total amount, the larger the dosage required.

[0066] The safety redundancy coefficient is an amplification factor reserved to compensate for actual engineering deviations such as water flow fluctuations and uneven mixing of reagents. Its value range is preferably 1.1 to 1.3. For example, it can be 1.3 in the scenario of chemical wastewater with large water quality fluctuations, and 1.1 in the scenario of relatively stable water quality.

[0067] The scale inhibitor complexation reaction efficiency coefficient is the probability ratio of the effective chelating groups in the scale inhibitor to the calcium ions that actually undergo a complexation blocking reaction. Due to the existence of steric hindrance and competitive reactions in the actual reaction, this coefficient is usually less than 1, and the preferred value range is 0.85 to 0.95.

[0068] The effective concentration of scale inhibitor is the mass percentage of the active ingredient with chelating function in the added composite scale inhibitor stock solution. For example, for a composite formulation composed of polyepoxysuccinic acid, hydroxyethylidene diphosphonic acid and nano calcium carbonate, its effective concentration CJ is usually between 0.2 and 0.5 (i.e., 20% to 50%).

[0069] The scale inhibitor dosage is the volume of composite scale inhibitor solution to be injected into the calcification reactor per hour, usually in L / h. It is calculated by the treatment terminal by substituting the wastewater calcium hardness and wastewater influent flow rate into the scale inhibitor model.

[0070] Step S402: Based on the calcium hardness of the wastewater, find the corresponding target dissolved inorganic carbon in the preset calcium hardness dissolved inorganic carbon correspondence.

[0071] The relationship between calcium hardness and dissolved inorganic carbon is the correspondence between different calcium hardness levels and the target dissolved inorganic carbon concentration. Under different calcium hardness levels, the minimum inorganic carbon concentration required to maintain the precipitation of calcium carbonate microcrystals without macroscopic precipitation is different. When the calcium hardness is between 1500 and 2500 mg / L, the target dissolved inorganic carbon concentration is 120 to 150 mg / L; when the calcium hardness is between 2500 and 4000 mg / L, the target dissolved inorganic carbon concentration is 150 to 180 mg / L; and when the calcium hardness is above 4000 mg / L, the target dissolved inorganic carbon concentration is 180 to 220 mg / L. The operator will create a mapping table to match the calcium hardness with the target dissolved inorganic carbon concentration.

[0072] The target dissolved inorganic carbon is to meet the requirements of calcification for hardening removal and pH stability. The optimal inorganic carbon concentration that needs to be maintained in the calcification reactor is obtained by the treatment terminal by looking up the mapping table corresponding to the calcium hardness of the wastewater in the calcium hardness-dissolved inorganic carbon correspondence.

[0073] Step S403: Calculate the target dissolved inorganic carbon, wastewater hydrogen ion concentration, and wastewater total alkalinity based on the preset dissolved inorganic carbon model to generate the dissolved inorganic carbon deviation.

[0074] The dissolved inorganic carbon model is used to calculate the deviation of dissolved inorganic carbon, and its specific expression is as follows: .

[0075] In the formula, To dissolve the deviation of inorganic carbon, To dissolve inorganic carbon, The total alkalinity of the wastewater. This refers to the hydrogen ion concentration in the wastewater. This is the preset first-order dissociation constant of carbonic acid. This is the preset second-order dissociation constant of carbonic acid.

[0076] The microscopic mechanism of this model lies in the fact that dissolved carbon dioxide in water is not entirely converted into carbonate ions, which can effectively promote the precipitation of microcrystals, but rather into CO2, H2CO, and HCO3-. - and CO3 -2 The four forms coexist dynamically, and the concentration of hydrogen ions in the wastewater directly determines the distribution ratio of these four forms. and The thermodynamic constants that describe this distribution are precisely those of the thermodynamic constants. and These are not fixed values; they drift significantly with changes in water temperature, for example, at 25°C. Approximately 4.45 × 10 -7 However, a shift occurs at 40℃. Therefore, when executing this model, the processing terminal dynamically retrieves the water temperature data at the current temperature based on the water temperature data synchronously detected by the multi-parameter water quality sensor. and Numerical values ​​are substituted into calculations to determine the true inorganic carbon deficit. If a crude, fixed-coefficient approach is used to add carbon dioxide, large amounts of carbon dioxide will escape in a free gaseous state under low-temperature or high-pH conditions. This not only fails to form microcrystals but also wastes reagents and causes secondary greenhouse gas pollution. Conversely, under high-temperature or low-pH conditions, it may lead to an excess of inorganic carbon, causing macroscopic scaling. Only through precise calculations using this model can we ensure that the introduced carbon dioxide precisely fills the deficit, achieving targeted calcium ion transfer.

[0077] Dissolved inorganic carbon deviation is the gap between the actual amount of inorganic carbon in the current wastewater and the target amount of inorganic carbon required to achieve targeted calcium removal. This gap is the amount that needs to be made up by introducing carbon dioxide. It is calculated by substituting the target dissolved inorganic carbon, wastewater hydrogen ion concentration, and wastewater total alkalinity into the dissolved inorganic carbon model at the treatment terminal.

[0078] Step S404: Calculate the dissolved inorganic carbon deviation and wastewater influent flow rate based on the preset carbon dioxide model to generate the carbon dioxide dosage.

[0079] The carbon dioxide model is used to calculate carbon dioxide emissions, and its specific expression is as follows: .

[0080] In the formula, This refers to the amount of carbon dioxide emitted. The preset carbon dioxide dissolution utilization coefficient, This refers to the wastewater influent flow rate. To address the deviation in dissolving inorganic carbon.

[0081] The model determines the total amount of carbon source that needs to be supplemented by multiplying the influent flow rate by the deviation of dissolved inorganic carbon. Then, it determines the final amount of carbon dioxide to be added by combining the carbon dioxide dissolution utilization coefficient and the mass-volume conversion.

[0082] The carbon dioxide dissolution utilization coefficient is the proportion of carbon dioxide gas that actually dissolves in the wastewater to be treated and participates in the reaction after being sprayed from the aeration nozzle. Due to bubble escape and mass transfer resistance, this coefficient is usually less than 1, and the preferred value range is 0.6 to 0.8.

[0083] The carbon dioxide dosage is the standard volume of carbon dioxide gas that needs to be introduced into the calcification reactor per hour, usually in m³ / h. It is calculated by the treatment terminal by substituting the dissolved inorganic carbon deviation and wastewater influent flow rate into the carbon dioxide model.

[0084] Step S405: Add composite scale inhibitor and carbon dioxide to the wastewater to be treated according to the dosage of scale inhibitor and carbon dioxide to target the removal of calcium.

[0085] In this process, after determining the dosage of scale inhibitor and carbon dioxide, the treatment terminal converts the dosage of scale inhibitor and carbon dioxide into corresponding opening commands for the metering pump and regulating valve, thereby precisely driving the dosing pump and carbon dioxide flow meter to accurately execute the dosing action, thus removing calcium from the wastewater to be treated.

[0086] Reference Figure 5 The steps for membrane concentration of the pretreated wastewater to achieve water-salt separation based on the pretreatment completion trigger signal include: Step S500: Based on the pretreatment completion trigger signal, pressurize the wastewater to be treated and pass it through a preset reverse osmosis membrane module to produce freshwater and wastewater.

[0087] Once the processing terminal receives the pretreatment completion trigger signal, it indicates that the wastewater can be concentrated using membrane treatment. At this point, the wastewater needs to be pressurized first, forcing it through the reverse osmosis membrane module to separate freshwater (TDS ≤ 300 mg / L) and wastewater (TDS between 120,000 and 180,000 mg / L). For specific methods, refer to [link to relevant documentation]. Figure 6 The process involves using fresh water for salt recovery and wastewater for pressurization.

[0088] The reverse osmosis membrane module adopts an antifouling modified reverse osmosis membrane module with salt-resistant polyamide as the base membrane and a polyethylene glycol-graphene composite coating (thickness 30-50nm) on the surface. The coating has superhydrophilic properties (water contact angle ≤25°), which can reduce the adsorption of salt scale and organic matter, and reduce the membrane fouling rate by more than 50%. At the same time, it adopts a "2-stage series + 1-stage parallel" structure, and the number of membrane elements in a single stage can be flexibly adjusted according to the treatment capacity. The operating pressure is stably controlled at 55-65 bar, the concentration ratio can reach 8-12 times, and the TDS of the concentrate can reach up to 180,000 mg / L. The "2-stage series + 1-stage parallel" structure is as follows: Stage 1 (parallel stage): The inlet and outlet water ends of the two membrane modules (Group A and Group B) are connected respectively. The high-pressure inlet water is evenly distributed to Groups A and B for preliminary concentration. The product water produced by the two groups is combined and sent directly for salt recovery. The concentrate produced by the two groups is also combined to form a primary concentrated concentrate. This design effectively increases the total treated water volume and reduces the load on a single membrane module without increasing the system pressure.

[0089] Section 2 (Series Section): The combined concentrate from the parallel section is introduced into the third membrane module (Group C) as its feed water. Group C further concentrates the concentrate that has already been concentrated once. The resulting permeate, along with the permeate from Groups A and B, is sent for salt recovery. The discharged concentrate is the final high-concentration concentrate, which is sent to the energy recovery unit to pressurize the wastewater to be treated. This design significantly improves the final concentration ratio and water recovery rate of the system through the re-treatment of the concentrate.

[0090] Step S501: Obtain the real-time operating flux of the reverse osmosis membrane module.

[0091] Among them, the real-time operating flux is the flux of the reverse osmosis membrane module, which is obtained by detecting the operating flux of the reverse osmosis membrane module through the membrane flux monitoring module and sent to the processing terminal.

[0092] Step S502: Determine whether the real-time operating throughput meets the requirements of the preset throughput warning threshold.

[0093] The flux warning threshold is the threshold for the percentage decrease in flux of the reverse osmosis membrane module. When scale or organic matter begins to adhere to the membrane surface, the water flow penetration resistance increases, and the real-time operating flux will inevitably show a decreasing trend. Taking 15% as an example, this is the golden ratio point that triggers the self-cleaning action. At this time, the fouling is still in the early stage of reversibility and can be easily removed by low-pressure hydraulic flushing. The flux warning threshold should not exceed the standard flux warning threshold.

[0094] The processing terminal calculates the real-time flux decrease ratio based on the real-time operating flux, thereby determining whether the real-time flux decrease ratio is not greater than the flux warning threshold, and thus determining whether the reverse osmosis membrane module needs to be backwashed.

[0095] Step S5021: If the conditions are met, the wastewater to be treated is pressurized and passed through a preset reverse osmosis membrane module to produce fresh water and wastewater.

[0096] If the treatment terminal determines that the real-time flux decrease ratio is not greater than the flux warning threshold, it indicates that the reverse osmosis membrane module is in a clean state. Therefore, the wastewater to be treated continues to be pressurized, thereby producing fresh water and wastewater through the reverse osmosis membrane module.

[0097] Step S5022: If not met, backwash the reverse osmosis membrane module until the real-time operating flux meets the flux warning threshold.

[0098] If the treatment terminal determines that the real-time flux decrease is greater than the flux warning threshold, it indicates that the reverse osmosis membrane module surface is severely fouled. Therefore, the treatment terminal activates the backwash command, using depressurized wastewater as the flushing water source. The pressure of this depressurized wastewater is 0.8 to 1.2 bar, which meets the pressure requirements for low-pressure backwashing. No additional backwash booster pump is required. The depressurized wastewater permeates in reverse from the freshwater side of the membrane, washing away the initial loose scale and colloids attached to the membrane surface and restoring the membrane flux. Since the flushing water source itself is freshwater that has been filtered through the membrane, its water quality is clean and will not cause secondary blockage of the membrane pores. The entire backwashing process does not require shutdown or the introduction of chemical cleaning agents, extending the traditional chemical cleaning cycle from once a week to six months or even longer. The membrane life is extended to 2 to 3 years, significantly reducing maintenance consumable costs and downtime losses.

[0099] Reference Figure 6 The steps for pressurizing the wastewater to be treated and passing it through a preset reverse osmosis membrane module to produce freshwater and wastewater based on a pretreatment completion trigger signal include: Step S600: Based on the pretreatment completion trigger signal, control the preset pressure exchanger to transmit the wastewater pressure to the wastewater to be treated to produce pressurized wastewater and depressurized wastewater.

[0100] The concentrated water (i.e. wastewater) discharged from the membrane concentration unit still carries extremely high pressure potential energy (usually between 45 and 55 bar). After the treatment terminal receives the pretreatment completion trigger signal, the treatment terminal uses a pressure exchanger to transfer the wastewater pressure to the wastewater to be treated, which can greatly reduce the energy consumption required for active pressurization. Thus, the wastewater to be treated is pre-pressurized to obtain pressurized wastewater, and the wastewater after pressure transfer becomes depressurized wastewater. The depressurized wastewater is used to backwash the reverse osmosis membrane module.

[0101] A pressure exchanger is a device that transfers the pressure of wastewater to the wastewater to be treated. Internally, it employs a piston-type hydraulic transmission structure. High-pressure concentrate enters from one end, pushing the piston. The other end of the piston directly compresses the atmospheric-pressure wastewater to be treated. Through hydraulic coupling via oil or water circuits, the pressure potential energy of the concentrate is seamlessly transferred to the wastewater, causing it to jump directly from atmospheric pressure to a pressurized state, reaching 40 to 50 bar. The core advantage of this process lies in its "no mechanical linkage," meaning the entire pressure transfer process relies entirely on fluid-hydraulic coupling, completely eliminating the impellers, gears, or bearings essential mechanical transmission components found in traditional energy recovery devices. It should be understood that while this embodiment illustrates a piston-type hydraulic transmission structure, other embodiments may also employ a rotary fluid pressure exchange structure, as long as the function of directly transmitting pressure without mechanical wear parts is satisfied. This design without mechanical linkage fundamentally eliminates the efficiency degradation and frequent seal replacement problems caused by mechanical wear, resulting in a long-term stable energy recovery efficiency of over 90% and a significantly reduced maintenance frequency. Meanwhile, after the concentrated water is pressurized, its own pressure decreases significantly, producing depressurized wastewater with a pressure of only 0.8 to 1.2 bar. This depressurized wastewater is not directly discharged, but is introduced into a low-pressure concentrated water buffer tank for temporary storage, serving as a high-quality water source for subsequent backwashing, thus achieving the dual extraction of water and pressure resources.

[0102] Step S601: Obtain the pressure transfer pressure of the pressurized wastewater to be treated.

[0103] The pressure transmission pressure is the actual pressure of the wastewater to be treated after pressurization. The pressure of the pressurized wastewater is collected in real time by a high-precision pressure sensor installed on the outlet pipe of the pressure exchanger and sent to the treatment terminal.

[0104] Step S602: Calculate the difference between the preset target pressure and the boost pressure to generate additional pressure.

[0105] The target pressure is the optimal driving pressure required for the reverse osmosis membrane module to achieve 8 to 12 times higher concentration, typically set between 55 and 65 bar.

[0106] The additional pressure is the pressure that needs to be actively increased for the wastewater to be treated, which is obtained by the treatment terminal by calculating the difference between the target pressure and the pressure transmitted through the booster.

[0107] Step S603: Pressurize the wastewater to be treated by applying additional pressure and pass it through the reverse osmosis membrane module to produce fresh water and wastewater.

[0108] In this process, after determining the additional pressure, the treatment terminal generates a frequency conversion command based on the additional pressure and sends the command to the staged booster pump, thereby operating in a pressure-replenishing mode to further increase the pressure of the wastewater to be treated to the target pressure, and then send it into the reverse osmosis membrane module to produce fresh water and wastewater.

[0109] Reference Figure 7 The steps for salt recovery from the product water after water-salt separation based on the trigger signal of membrane concentration completion to achieve water resource recycling include: Step S700: Obtain the type of compliant permeate based on the membrane concentration completion trigger signal.

[0110] Once the processing terminal receives the membrane concentration completion trigger signal, it indicates that the wastewater to be treated has completed the membrane concentration treatment, achieving the separation of freshwater and wastewater. At this time, the qualified product water type of the freshwater is detected to provide data support for subsequent salt recovery of the freshwater.

[0111] The compliant product water type refers to the freshwater obtained after water-salt separation, mainly divided into two categories: one is a mixed product water containing a large amount of divalent salts (such as sodium sulfate) and monovalent salts (such as sodium chloride); the other is a single high-salt product water dominated by a single salt (such as pure high-concentration sodium chloride). It should be understood that although this embodiment lists the typical combination of sodium sulfate and sodium chloride, in other embodiments, the product water type can also be a mixture of nitrates and chlorides, as long as the system can determine whether salt separation is necessary. After detecting the freshwater using a multi-parameter water quality sensor, the product water type is classified according to the ion type and concentration. When the ion concentration reaches a set threshold, it can be clearly determined that the freshwater contains that ion.

[0112] Step S701: Based on the type of qualified produced water, perform salt recovery on the produced water after water-salt separation to produce the final produced water.

[0113] After determining the type of compliant wastewater, salt is recovered from the wastewater after water-salt separation based on the type of compliant wastewater, yielding solid salt products and final wastewater. Specific methods are described in [reference needed]. Figure 8 The steps.

[0114] Step S702: Obtain the final product water quality parameters.

[0115] Among them, the water quality parameter of the produced water is the TDS value of the final produced water, which is obtained by detecting the final produced water with an online TDS analyzer and sending it to the treatment terminal.

[0116] Step S703: Determine whether the product water quality parameters meet the preset requirements for compliant product water quality parameters.

[0117] The quality parameter for compliant product water is the TDS concentration at which it can be reused in the network. Taking 300 mg / L as an example, this threshold is set based on the common influent standards for industrial circulating cooling water and boiler feedwater. If the TDS exceeds 300 mg / L, the reused water will pose a risk of corrosion and scaling to the production equipment. The requirement for compliant product water quality parameters is that they should not exceed the compliant product water quality parameters.

[0118] The processing terminal determines whether the water quality parameters of the produced water are not greater than the standard water quality parameters for produced water, thereby determining whether the final produced water can be reused.

[0119] Step S7031: If the conditions are met, the final produced water will be sent into the preset reuse network to achieve water resource recycling.

[0120] If the treatment terminal determines that the water quality parameters of the produced water are not greater than the water quality parameters of the compliant produced water, it indicates that the water quality of the final produced water meets the standards. Therefore, the valves of the reuse pipeline are opened to transport the final produced water to the reuse pipeline, thereby realizing the closed-loop reuse of water resources and ensuring that the overall system reuse rate remains stable at over 85%.

[0121] Step S7032: If not met, the final permeate water shall be re-concentrated using a membrane.

[0122] If the treatment terminal determines that the quality parameters of the produced water are greater than the standard quality parameters of the produced water, it indicates that a trace amount of salt was carried into the condensate during the salt recovery process. In this case, the final produced water will be concentrated again using a membrane.

[0123] Reference Figure 8 The steps for recovering salt from the water-salt separation product water to produce final product water, based on the type of qualified product water, include: Step S800: Determine whether the qualified product water type meets the requirements of the preset multi-salt mixed product water type.

[0124] Among them, the multi-salt mixed product water type refers to the type of product water containing multiple salts. The requirements for the multi-salt mixed product water type are consistent with those for the multi-salt mixed product water type.

[0125] By determining whether the type of compliant produced water is consistent with the type of multi-salt mixed produced water through the processing terminal, it can be determined whether the produced water after water-salt separation contains multiple salts or a single salt, providing data support for determining how to recover salt in the future.

[0126] Step S801: If not, the product water after water-salt separation is directly evaporated and crystallized to produce crystalline salt and final product water.

[0127] If the treatment terminal determines that the type of compliant permeate is inconsistent with the type of multi-salt mixed permeate, it indicates that the permeate after water-salt separation contains a single salt. Therefore, the treatment terminal controls the valve to open and sends the permeate after water-salt separation into the MVR evaporation and crystallization module. The MVR evaporation and crystallization module uses mechanical vapor recompression technology to increase the pressure and temperature of secondary steam through a compressor and sends it back into the evaporator as heating steam. It makes full use of the waste heat carried by the membrane concentration concentrate itself for preheating the feed. This direct crystallization short-process design eliminates the energy consumption and equipment investment of intermediate separation links, making the evaporation energy consumption more than 60% lower than that of traditional multi-effect evaporation, and directly producing high-purity solid salt products and condensate (i.e., final permeate).

[0128] Step S802: If the conditions are met, control the preset nanofiltration desalination module to separate salts in the product water after water-salt separation, so as to produce water with a single salt content.

[0129] If the treatment terminal determines that the type of compliant produced water is consistent with the type of multi-salt mixed produced water, it indicates that the produced water after water-salt separation contains multiple salts. Therefore, it is necessary to control the nanofiltration salt separation module to separate the salts in the produced water after water-salt separation to obtain a single salt-rich produced water, which facilitates salt recovery.

[0130] A nanofiltration desalination module is a device that separates permeate into permeate containing a single salt. The module is filled with nanofiltration membrane elements that have a high selective rejection rate for divalent ions. Its microscopic separation mechanism lies in the fact that the nanofiltration membrane surface is negatively charged, and its pore size is between that of reverse osmosis and ultrafiltration. When multi-salt concentrate flows through the membrane surface, sulfate ions, carrying a divalent negative charge, are strongly electrostatically repelled by the membrane surface, and their larger molecular size is also blocked by the physical pore size, thus being almost completely retained on the concentrate side. Meanwhile, chloride ions, carrying a monovalent negative charge, are able to permeate in large quantities to the permeate side due to weak electrostatic repulsion and their smaller size. Through this dual sieving effect of charge and size, the originally mixed multi-salt concentrate is precisely separated into two streams: one is a divalent ion-retaining liquid rich in sodium sulfate, and the other is a monovalent ion-permeable liquid rich in sodium chloride, thereby achieving the decoupling of the complex salt system and the production of a single salt-rich permeate.

[0131] Step S8021: Evaporate and crystallize the single salt-rich product water to produce crystalline salt and final product water.

[0132] In this process, after the nanofiltration salt separation module produces a single salt-rich product, the treatment terminal introduces the single salt-rich product into different evaporation loops of the MVR evaporation and crystallization module for independent evaporation and crystallization, ultimately producing two high-value crystalline salt products: anhydrous sodium sulfate (purity ≥98%) and industrial salt (purity ≥97%). At the same time, condensate is produced as the final product.

[0133] Based on the same inventive concept, embodiments of this application provide a low-pressure, high-concentration system for high-salinity wastewater, comprising: The acquisition module is used to acquire water quality detection parameters, pretreatment completion trigger signal, membrane concentration completion trigger signal, filtered water quality parameters, real-time operating flux, pressure transmission pressure, compliant product water type, and product water quality parameters. A memory for storing a program for a low-pressure, high-concentration method for high-salt wastewater; The processor can load and execute programs in memory to implement a low-pressure, high-concentration method for high-salt wastewater.

[0134] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional modules is used as an example. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, device, and unit described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0135] This application provides a computer-readable storage medium storing a computer program that can be loaded by a processor and executed as a method for low-pressure, high-concentration of high-salt wastewater.

[0136] Computer storage media include, for example, USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, optical disks, and other media that can store program code.

[0137] Based on the same inventive concept, this application provides a smart terminal, including a memory and a processor. The memory stores a computer program that can be loaded and executed by the processor to perform a low-pressure, high-concentration method for high-salt wastewater.

[0138] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional modules is used as an example. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, device, and unit described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0139] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Any feature disclosed in this specification (including the abstract and drawings) may be replaced by other equivalent or similar features unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is only one example of a series of equivalent or similar features.

Claims

1. A method for low-pressure, high-concentration of high-salinity wastewater, characterized in that, include: Obtain the water quality testing parameters of the wastewater to be treated; Based on water quality testing parameters, the wastewater to be treated is pretreated in different categories to achieve targeted pollution removal, and a pretreatment completion trigger signal is obtained; Based on the pretreatment completion trigger signal, the pretreated wastewater is subjected to membrane concentration treatment to achieve water-salt separation, and the membrane concentration completion trigger signal is obtained. Salt recovery is performed on the product water after water-salt separation based on the trigger signal of membrane concentration completion to achieve water resource recycling. The steps for targeted pollution removal by pre-treating wastewater according to water quality testing parameters include: Determine whether the water quality testing parameters meet the preset requirements for calcium- and silicon-rich water quality parameters; If it does not meet the requirements, the wastewater to be treated shall be filtered. If the conditions are met, the wastewater to be treated will be pretreated according to the water quality testing parameters to achieve targeted pollution removal, and the pretreated wastewater will be filtered. Obtain the filtered water quality parameters; When the filtered water quality parameters do not meet the preset water quality standards, the wastewater to be treated is re-pretreated according to different parameters until the filtered water quality parameters meet the water quality standards. The steps for pretreatment of wastewater to achieve targeted pollution removal based on water quality testing parameters include: Determine if the water quality test parameters are within the preset range of single silica water quality parameters, preset range of single calcium water quality parameters, or preset range of mixed water quality parameters. If the water quality parameters are within the range of single silicon, the preset silicon adsorption column is controlled to adsorb silicon into the wastewater to be treated in order to remove silicon elements in a targeted manner. If the water quality parameters are within the range of single calcium, then a pre-set composite scale inhibitor and carbon dioxide are added to the wastewater to be treated to target and remove calcium. If the water quality parameters are within the range of mixed water quality, the wastewater to be treated should be pretreated by mixing to target the removal of calcium and silicon elements. The steps of adding a pre-set composite scale inhibitor and carbon dioxide to the wastewater to target the removal of calcium include: The wastewater calcium hardness, wastewater influent flow rate, wastewater hydrogen ion concentration, and wastewater total alkalinity are determined based on water quality testing parameters. The scale inhibitor dosage is calculated based on the pre-set scale inhibitor model, which calculates the calcium hardness of the wastewater and the influent flow rate. The target dissolved inorganic carbon is found in the preset calcium hardness-dissolved inorganic carbon correspondence based on the calcium hardness of the wastewater. Based on a pre-defined dissolved inorganic carbon model, the target dissolved inorganic carbon, wastewater hydrogen ion concentration, and wastewater total alkalinity are calculated to generate a dissolved inorganic carbon deviation. The dissolved inorganic carbon deviation and wastewater influent flow rate are calculated based on a pre-set carbon dioxide model to generate the carbon dioxide dosage. Based on the dosage of scale inhibitor and carbon dioxide, a composite scale inhibitor and carbon dioxide are added to the wastewater to be treated to target the removal of calcium. The expression for the scale inhibitor model is: ； In the formula, This refers to the dosage of scale inhibitor. As a preset safety redundancy factor, For the calcium hardness of wastewater, This refers to the wastewater influent flow rate. This is the preset efficiency coefficient for the complexation reaction of the scale inhibitor. This is the preset effective concentration of the scale inhibitor; The expression for the dissolved inorganic carbon model is: ； In the formula, To dissolve the deviation of inorganic carbon, To dissolve inorganic carbon, The total alkalinity of the wastewater. This refers to the hydrogen ion concentration in the wastewater. This is the preset first-order dissociation constant of carbonic acid. This is the preset second-order dissociation constant of carbonic acid; The expression for the carbon dioxide model is: ； In the formula, This refers to the amount of carbon dioxide emitted. The preset carbon dioxide dissolution utilization coefficient, This refers to the wastewater influent flow rate. To address the deviation in dissolving inorganic carbon.

2. The method for low-pressure high-concentration of high-salinity wastewater according to claim 1, characterized in that, The steps for membrane concentration of the pretreated wastewater to achieve water-salt separation based on the pretreatment completion trigger signal include: Based on the pretreatment completion trigger signal, the wastewater to be treated is pressurized and passed through a preset reverse osmosis membrane module to produce freshwater and wastewater; the freshwater is used for salt recovery, and the wastewater is used for pressurization. Obtain the real-time operating flux of the reverse osmosis membrane module; Determine whether the real-time operating throughput meets the preset throughput warning threshold requirements; If the conditions are met, the wastewater to be treated will be pressurized and passed through a pre-set reverse osmosis membrane module to produce fresh water and wastewater. If it does not meet the requirements, the reverse osmosis membrane module will be backwashed until the real-time operating flux meets the flux warning threshold.

3. The method for low-pressure high-concentration of high-salinity wastewater according to claim 2, characterized in that, The steps for pressurizing the wastewater to be treated and passing it through a preset reverse osmosis membrane module to produce freshwater and wastewater based on the pretreatment completion trigger signal include: Based on the pretreatment completion trigger signal, the preset pressure exchanger is controlled to transmit the wastewater pressure to the wastewater to be treated to produce pressurized wastewater and depressurized wastewater; the depressurized wastewater is used to backwash the reverse osmosis membrane module; Obtain the pressure transmission pressure of the pressurized wastewater to be treated; The difference between the preset target pressure and the boost pressure is calculated to generate additional pressure. The wastewater to be treated is pressurized by adding extra pressure and passed through the reverse osmosis membrane module to produce fresh water and wastewater.

4. The method for low-pressure high-concentration of high-salinity wastewater according to claim 1, characterized in that, The steps for salt recovery from the product water after water-salt separation based on the trigger signal of membrane concentration completion to achieve water resource recycling include: The type of compliant permeate is determined based on the trigger signal indicating completion of membrane concentration. Salt is recovered from the water after water-salt separation to produce final product water, depending on the type of product water that meets the standards. Obtain the final product water quality parameters; Determine whether the product water quality parameters meet the preset requirements for compliant product water quality parameters; If the conditions are met, the final produced water will be sent to the pre-designed reuse network to achieve water resource recycling. If it does not meet the requirements, the final product water will be re-concentrated using a membrane.

5. The method for low-pressure high-concentration of high-salinity wastewater according to claim 4, characterized in that, The steps for recovering salt from the water after water-salt separation to produce final product water, based on the type of qualified product water, include: Determine whether the qualified product water type meets the preset requirements for the multi-salt mixed product water type; If not, the product water after water-salt separation is directly evaporated and crystallized to produce crystalline salt and final product water; If the conditions are met, the preset nanofiltration desalination module will be controlled to separate salts in the product water after water-salt separation, so as to produce water with a single salt content. Evaporation and crystallization are performed on a single salt-rich product water to produce crystalline salt and final product water.

6. A low-pressure, high-concentration system for high-salinity wastewater, characterized in that, include: The acquisition module is used to acquire water quality testing parameters, pretreatment completion trigger signal, and membrane concentration completion trigger signal; A memory for storing a program for a low-pressure, high-concentration method for high-salt wastewater as described in any one of claims 1 to 5; The processor and the program in the memory can be loaded and executed by the processor to implement the low-pressure high-concentration method for high-salt wastewater as described in any one of claims 1 to 5.

Images