A device and method for producing mineralized drinking water by nanofiltration coupled with electrodialysis

Abstract

The application relates to a device and method for producing mineralized drinking water by coupling nanofiltration and electrodialysis, and relates to the technical field of water treatment. The device solves the problem that nanofiltration membranes remove a variety of pollutants while removing a variety of natural mineral ions beneficial to human bodies, and the problem that the separation performance of nanofiltration membranes is insufficient in matching the separation target. The device comprises the following steps: introducing, into a nanofiltration unit, pretreated water containing ions and potential organic pollutants through the inlet of the nanofiltration unit; obtaining first dilute water and first concentrated water through nanofiltration separation; introducing the first dilute water and the first concentrated water into a first reverse electrodialysis unit respectively; performing ion redistribution in the first reverse electrodialysis unit; introducing second concentrated water after the redistribution into a second reverse electrodialysis unit; performing ion distribution with second water treated by a nanofiltration-gravity flow ultrafiltration system; obtaining second effluent flowing out of the second reverse electrodialysis unit; and returning third concentrated water obtained after the distribution to the nanofiltration unit. The application is applied to the field of drinking water production.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to an apparatus for producing mineralized drinking water using nanofiltration coupled with electrodialysis. Background Technology

[0002] In recent years, with the increasing demands for drinking water quality, nanofiltration technology has developed rapidly in the field of urban drinking water treatment in my country. Nanofiltration membranes can effectively remove organic pollutants and some inorganic ions from water, but they also remove some beneficial natural mineral ions, resulting in low mineral ion content in the produced water, which is detrimental to human health. To address this issue, solutions such as developing new nanofiltration membrane materials or adding mineralized filter cartridges have been proposed. However, the development cycle for new membrane materials is long and the cost is high, while mineralized filter cartridges contain only a single type of mineral and are artificially produced, requiring further research into their safety and health benefits.

[0003] Nanofiltration concentrate, produced during the nanofiltration process, has a high concentration of mineral ions and comes from a more natural and reliable source, making it a promising source for replenishing ions in nanofiltration effluent. However, current technologies cannot efficiently separate and controllably add mineral ions to nanofiltration concentrate, failing to meet residents' demands for high-quality drinking water. Therefore, there is an urgent need to develop a novel water treatment technology capable of efficiently separating organic matter and mineral ions, and controllably adding mineral ions, to produce mineralized drinking water with appropriate mineral content.

[0004] Regarding the issue of insufficient matching between the separation performance and separation targets of nanofiltration membranes, which remove multiple pollutants but also various beneficial natural mineral ions, several invention patents have been developed. For example:

[0005] CN114929370A discloses a method for providing purified and mineralized drinking water from contaminated freshwater or brackish water. This patent employs a reverse electrodialysis unit and an auxiliary reverse electrodialysis unit to perform ion distribution on nanofiltration concentrate, achieving controllable addition of mineral ions. However, this patent still faces the challenge of further simplifying the structure and operation of the device to make it easier to maintain and use.

[0006] CN111087095A discloses a method for preparing high-quality drinking water, which uses a combined process of "coagulation-short-process ultrafiltration-nanofiltration" to treat surface water, removing trace organic matter harmful to the human body while retaining most of the inorganic salts. However, this patent still has problems such as using low-desalination membrane elements and filters, resulting in a weak ability to remove pollutants from the water and selectively remove toxic and harmful ions. Summary of the Invention

[0007] This invention addresses the problem that nanofiltration membranes, while removing various pollutants, also remove many beneficial natural mineral ions, resulting in insufficient matching between nanofiltration membrane separation performance and separation targets. The invention proposes a device for producing mineralized drinking water using nanofiltration coupled with electrodialysis, the device comprising:

[0008] Nanofiltration unit, first reverse electrodialysis unit, shore filtration-gravity flow ultrafiltration unit and second reverse electrodialysis unit;

[0009] The pretreated influent containing ions and potential organic pollutants is introduced into the nanofiltration unit through the inlet. The nanofiltration separates the first freshwater and the first concentrated water, which then enter the first reverse electrodialysis unit. The first reverse electrodialysis unit redistributes ions from the introduced first freshwater and first concentrated water, using real-time water quality monitoring equipment and PLC control equipment to monitor the TDS of the freshwater and control the effluent TDS within the range of 120-200 mg / L. The effluent obtained after ion distribution exits the first reverse electrodialysis unit, while the redistributed second concentrated water enters the second reverse electrodialysis unit for ion distribution with the second river water treated by the bank filtration-gravity flow ultrafiltration system. The resulting second effluent exits the second reverse electrodialysis unit, and the third concentrated water obtained after distribution is returned to the nanofiltration unit.

[0010] Furthermore, a preferred method is proposed, wherein the water quality conditions of the pretreated influent containing ions and potential organic pollutants are as follows: the influent has micro-pollutants, algae, and emerging pollutants, and the TDS concentration of the concentrate produced by the nanofiltration unit is higher than 1000 mg / L, the permanganate index is higher than 6 mg / L, and no excessive perfluorinated compounds are detected in the raw water.

[0011] Furthermore, a preferred embodiment is proposed, wherein the device further includes a concentrate treatment unit disposed between the nanofiltration unit and the first reverse electrodialysis unit. The concentrate treatment unit selects an advanced oxidation or advanced reduction treatment method according to the organic pollution problem of the influent water. Specifically, when the permanganate index exceeds the limit value, advanced oxidation treatment is selected, and when excessive perfluorinated compounds are detected, advanced reduction treatment is selected.

[0012] Furthermore, a preferred embodiment is proposed in which the ion distribution of the first and second reverse electrodialysis units includes polarity reversal, with a reverse voltage applied when the voltage decreases by 20%.

[0013] Furthermore, a preferred embodiment is proposed in which the first reverse electrodialysis unit selects conventional reverse electrodialysis technology and assisted reverse electrodialysis technology according to the TDS level of the concentrate in the nanofiltration unit. When the TDS of the concentrate is lower than 1000 mg / L, an auxiliary voltage is applied in the direction of the natural salinity gradient to enhance ion transport. The voltage level is 0 to 6 V per membrane pair.

[0014] Furthermore, a preferred embodiment is proposed, wherein the treatment parameters of the nanofiltration unit are: operating pressure of 0.3-3 MPa, recovery rate of 70%-90% selected according to actual operating conditions, influent turbidity of the nanofiltration unit of less than 0.5 NTU, and pH range of 6.8-7.2.

[0015] Furthermore, a preferred method is proposed, wherein the processing parameters of the first reverse electrodialysis unit are: the turbidity of the concentrate influent is less than 0.1 NTU, the TDS of the influent is less than 5000 mg / L, and the operating flow rate is controlled in the range of 5-30 cm / s.

[0016] Furthermore, a preferred embodiment is proposed, wherein the treatment parameters of the shore filter-gravity flow ultrafiltration unit are: effluent turbidity controlled within 0.2 NTU, and effluent TDS in the range of 10-1000 mg / L.

[0017] Furthermore, a preferred embodiment is proposed: when the concentrated wastewater treatment unit selects advanced oxidation treatment, ozone or sodium hypochlorite is selected, and the ozone dosage is 0.8-2 times the COD. Mn The dosage of sodium hypochlorite is 0.8-1.5 times the COD. Mn When selecting advanced reduction treatment, UV-catalyzed sodium bisulfite reduction is chosen, with an addition amount of 6000-10000 times the molar concentration of perfluorinated compounds.

[0018] Based on the same inventive concept, the present invention also proposes a method for producing mineralized drinking water, said method being implemented based on the nanofiltration coupled electrodialysis apparatus for producing mineralized drinking water described in any of the preceding claims, said method comprising:

[0019] The raw water is nano-filtered, and the fresh water and concentrated water enter the first reverse electrodialysis unit for ion separation to obtain mineralized effluent. The concentrated water enters the second reverse electrodialysis unit and undergoes ion separation again with the river water that has been treated by bank filtration-gravity flow ultrafiltration. The resulting concentrated effluent is returned to the nanofiltration inlet. The river water after ion separation is used for landscape water or fire fighting water.

[0020] The advantages of this invention are:

[0021] 1. This invention organically couples nanofiltration technology with reverse electrodialysis technology. This coupling method fully leverages the advantages of both technologies, overcomes the limitations of traditional single technologies in mineralization and water quality control, and provides an innovative solution for the production of mineralized drinking water.

[0022] 2. Throughout the entire production process of this invention, the mineral ions are sourced from the water source itself, reducing the use of chemical reagents and the impact on the environment. The concentrated brine generated by the system is rationally treated and recycled, maximizing the utilization of ion resources, which is in line with the concept of sustainable development.

[0023] 3. Compared with traditional mineral water production methods, this invention has lower energy consumption. The synergistic effect of nanofiltration and reverse electrodialysis processes reduces energy costs;

[0024] 4. This invention can achieve efficient separation of organic matter and mineral ions, and can add mineral ions in an adjustable manner, thereby producing mineralized drinking water with appropriate mineral content to meet residents' demand for high-quality drinking water.

[0025] 5. This invention utilizes naturally sourced mineral ions in nanofiltration concentrate as an ion replenishment source, eliminating the need to develop new nanofiltration membrane materials or add mineralized filter cartridges, thus avoiding high R&D costs and safety and health issues related to artificial minerals.

[0026] 6. This invention employs multi-stage electrodialysis ion allocation technology, which can fully utilize the mineral ion resources in nanofiltration concentrate and river water, improve ion utilization, and reduce operating costs.

[0027] 7. The device of the present invention has a relatively simple structure, is easy to operate and maintain, and has high processing efficiency;

[0028] 8. This invention, through real-time water quality monitoring equipment and PLC control equipment, can accurately control the TDS of the effluent within a suitable range of 120-200 mg / L, ensuring that the mineral content of the produced water is moderate.

[0029] This invention is applied to the field of drinking water production. Attached Figure Description

[0030] Figure 1 The flow chart of the nanofiltration coupled electrodialysis device described in Embodiment 1 for the production of mineralized drinking water under normal operating conditions is shown.

[0031] Figure 2 The following is a flow chart of the nanofiltration coupled electrodialysis device described in Embodiment Eleven for the production of mineralized drinking water under unconventional operating conditions; in the figure, I1 represents the pretreated influent containing ions and potential organic pollutants, L1 is the first fresh water, H1 is the first concentrated water, E1 is the first effluent, E2 is the second effluent, R1 is the first river water, R2 is the second river water, and H3 is the third concentrated water.

[0032] Figure 3 This is a schematic diagram of the operation of the reverse electrodialysis and external electric field-assisted reverse electrodialysis device described in Embodiment Eleven. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0034] Implementation Method 1, see [link] Figure 1 This embodiment describes an apparatus for producing mineralized drinking water using nanofiltration coupled with electrodialysis. The apparatus includes:

[0035] Nanofiltration unit, first reverse electrodialysis unit, shore filtration-gravity flow ultrafiltration unit and second reverse electrodialysis unit;

[0036] The pretreated influent containing ions and potential organic pollutants is introduced into the nanofiltration unit through the inlet. The nanofiltration separates the first freshwater and the first concentrated water, which then enter the first reverse electrodialysis unit. The first reverse electrodialysis unit redistributes ions from the introduced first freshwater and first concentrated water, using real-time water quality monitoring equipment and PLC control equipment to monitor the TDS of the freshwater and control the effluent TDS within the range of 120-200 mg / L. The effluent obtained after ion distribution exits the first reverse electrodialysis unit, while the redistributed second concentrated water enters the second reverse electrodialysis unit for ion distribution with the second river water treated by the bank filtration-gravity flow ultrafiltration system. The resulting second effluent exits the second reverse electrodialysis unit, and the third concentrated water obtained after distribution is returned to the nanofiltration unit.

[0037] In practical applications, the number of membrane modules and stages in a nanofiltration unit are determined based on the treatment scale and recovery rate. The number of ion exchange membrane pairs in the first and second reverse electrodialysis units ranges from 10 to 500 pairs depending on the unit size.

[0038] This embodiment, by introducing a reverse electrodialysis unit, enables the controlled addition of mineral ions to the water. Especially in the combined application of the first and second reverse electrodialysis units, the concentration of mineral ions in the water can be precisely adjusted as needed. This ensures that the purified water not only removes harmful pollutants but also retains and regulates beneficial mineral components (such as calcium and magnesium). This avoids the problem of beneficial mineral ion loss commonly found in traditional nanofiltration membrane technology.

[0039] By using real-time water quality monitoring equipment and PLC control equipment, an invention has been developed that can accurately monitor and adjust the total dissolved solids (TDS) content in water, ensuring that the TDS of the final effluent is controlled within the range of 120-200 mg / L. This control mechanism ensures that the taste, mineral content, and health benefits of the purified water meet the standards for human drinking water, and can be flexibly adjusted according to needs.

[0040] The device, through the combination of multi-stage reverse electrodialysis units and a shore-gravity flow ultrafiltration system, not only improves water quality and safety but also optimizes the mineral ion content in the water during the multi-stage distribution process. In each reverse electrodialysis unit, the water undergoes multiple ion redistribution processes, removing harmful ions while retaining the necessary beneficial mineral ions, further enhancing water quality.

[0041] Implementation Method 2: This implementation method further defines the device for producing mineralized drinking water by nanofiltration coupled with electrodialysis as described in Implementation Method 1. The water quality conditions of the pretreated influent containing ions and potential organic pollutants are as follows: the influent contains micro-pollutants, algae, and emerging pollutants, and the TDS concentration of the concentrate produced by the nanofiltration unit is higher than 1000 mg / L, the permanganate index is higher than 6 mg / L, and no excessive perfluorinated compounds are detected in the raw water.

[0042] Implementation Method 3: This implementation method further defines the apparatus for producing mineralized drinking water using nanofiltration coupled with electrodialysis as described in Implementation Method 1. The apparatus further includes a concentrate treatment unit, which is disposed between the nanofiltration unit and the first reverse electrodialysis unit. The concentrate treatment unit selects an advanced oxidation or advanced reduction treatment method based on the organic pollution problem of the influent water. Specifically, when the permanganate index exceeds the limit, advanced oxidation treatment is selected; when excessive perfluorinated compounds are detected, advanced reduction treatment is selected.

[0043] In this embodiment, by introducing a concentrated water treatment unit, the device can perform targeted treatment based on the characteristics of different pollutants in the water (such as organic pollutants, permanganate index, and perfluorinated compounds). This flexible treatment method ensures efficient removal of various pollutants during the water purification process: for water sources with high permanganate indexes, strong oxidants can oxidize organic pollutants in the water, reducing their concentration and ensuring safer water quality. For water sources containing perfluorinated compounds, advanced reduction treatment methods can effectively decompose these harmful substances, preventing them from posing potential threats to human health.

[0044] The introduction of a concentrated wastewater treatment unit allows for more refined water treatment. Traditional single-method water treatment may struggle to effectively address the presence of different types of contaminants in the influent, but this device can select different treatment methods based on the specific type of contaminant. This flexible selection efficiently removes harmful substances from the water, ensuring that the water quality meets drinking water standards.

[0045] Implementation Method 4: This implementation method further defines the apparatus for producing mineralized drinking water by nanofiltration coupled electrodialysis as described in Implementation Method 1. The ion distribution of the first reverse electrodialysis unit and the second reverse electrodialysis unit includes polarity reversal, and a reverse voltage is applied when the voltage decreases by 20%.

[0046] Implementation Method 5: This implementation method further defines the device for producing mineralized drinking water by nanofiltration coupled with electrodialysis as described in Implementation Method 4. The first reverse electrodialysis unit selects conventional reverse electrodialysis technology and assisted reverse electrodialysis technology according to the TDS level of the concentrate in the nanofiltration unit. When the TDS of the concentrate is lower than 1000 mg / L, an auxiliary voltage is applied in the direction of the natural salinity gradient to enhance ion transport. The voltage level is 0-6 V / membrane pair.

[0047] This embodiment will be explained in conjunction with Embodiment 4. By adjusting the electrode polarity of the reverse electrodialysis unit, applying a reverse voltage when the voltage decreases by 20% helps optimize ion migration during the electrodialysis process, reducing ion accumulation and improving efficiency. This polarity reversal and voltage variation design ensures more efficient current and ion transport during the electrodialysis process, especially when the concentrate TDS is low, enhancing ion transport and improving the quality of mineralized water. When the concentrate TDS is below 1000 mg / L, auxiliary reverse electrodialysis technology is used, applying an auxiliary voltage (0-6V / membrane pair) along the natural salinity gradient direction, enhancing the ion transport capacity of low TDS water sources. This strategy is very effective when the water is soft and low in mineralization, further improving the mineralization level and taste of mineralized drinking water. By combining nanofiltration and reverse electrodialysis, the mineral content in the water can be precisely controlled, providing drinking water with moderate mineralization levels. Through the optimized design of the reverse electrodialysis unit, ion transport can be further enhanced, maintaining an appropriate mineral concentration in the water without sacrificing health standards. The application of reverse electrodialysis allows unwanted ions in water to be effectively removed while replenishing essential minerals, thereby improving the taste and health of the water.

[0048] Implementation Method Six: This implementation method further defines the device for producing mineralized drinking water by nanofiltration coupled with electrodialysis as described in Implementation Method One. The processing parameters of the nanofiltration unit are as follows: operating pressure is 0.3-3 MPa, recovery rate is selected according to actual operating conditions as 70%-90%, influent turbidity of the nanofiltration unit is less than 0.5 NTU, and pH is in the range of 6.8-7.2.

[0049] Implementation Method Seven: This implementation method further defines the device for producing mineralized drinking water by nanofiltration coupled with electrodialysis as described in Implementation Method One. The processing parameters of the first reverse electrodialysis unit are: the turbidity of the concentrate influent is less than 0.1 NTU, the TDS of the influent is less than 5000 mg / L, and the operating flow rate is controlled in the range of 5-30 cm / s.

[0050] Implementation Method 8: This implementation method further defines the device for producing mineralized drinking water by nanofiltration coupled with electrodialysis as described in Implementation Method 1. The treatment parameters of the shore filter-gravity flow ultrafiltration unit are: effluent turbidity controlled within 0.2 NTU, and effluent TDS in the range of 10-1000 mg / L.

[0051] This embodiment is described in conjunction with embodiments six and seven. The turbidity of the influent to the nanofiltration unit is below 0.5 NTU, ensuring good influent water quality, avoiding membrane fouling by particulate matter and suspended solids, and effectively removing most dissolved solids (TDS) and certain harmful substances (such as heavy metals and bacteria) from the water, thus improving drinking water safety. The reverse electrodialysis unit controls the turbidity of the concentrate influent below 0.1 NTU and the TDS below 5000 mg / L, helping to further reduce high-concentration dissolved substances in the water and achieve the salt and mineral balance required for mineralization. The pH range of the nanofiltration unit is controlled between 6.8 and 7.2 to ensure stable water pH and avoid potential health hazards from excessively acidic or alkaline water. This range is suitable for human drinking water standards and also ensures the normal operation of the equipment. The nanofiltration unit has a recovery rate of 70%-90%. Through optimized operation, water waste can be reduced, water utilization can be improved, and production efficiency and water quality stability can be guaranteed.

[0052] This device, through a combination of nanofiltration and electrodialysis, effectively removes harmful substances from water while retaining appropriate minerals and salinity. The final effluent TDS is controlled within the range of 10-1000 mg / L, meeting the standards for mineralized water. It not only retains beneficial minerals but also avoids health problems caused by excessively high or low salinity levels. The shore-filtration-gravity flow ultrafiltration unit controls the effluent turbidity to below 0.2 NTU, further improving water transparency and clarity, providing higher quality drinking water.

[0053] Implementation Method Nine: This implementation method further defines the apparatus for producing mineralized drinking water using nanofiltration coupled with electrodialysis as described in Implementation Method Three. When the concentrated water treatment unit selects advanced oxidation treatment, ozone or sodium hypochlorite is selected, and the ozone dosage is 0.8-2 times the COD. Mn The dosage of sodium hypochlorite is 0.8-1.5 times the COD. Mn When selecting advanced reduction treatment, UV-catalyzed sodium bisulfite reduction is chosen, with an addition amount of 6000-10000 times the molar concentration of perfluorinated compounds.

[0054] Implementation Method 10: A method for producing mineralized drinking water according to this implementation method, the method being implemented based on a nanofiltration coupled electrodialysis apparatus for producing mineralized drinking water as described in any one of Implementation Methods 1 to 9, the method comprising:

[0055] The raw water is nano-filtered, and the fresh water and concentrated water enter the first reverse electrodialysis unit for ion separation to obtain mineralized effluent. The concentrated water enters the second reverse electrodialysis unit and undergoes ion separation again with the river water that has been treated by bank filtration-gravity flow ultrafiltration. The resulting concentrated effluent is returned to the nanofiltration inlet. The river water after ion separation is used for landscape water or fire fighting water.

[0056] Implementation Method 11, see below Figure 2 and Figure 3 This embodiment describes a specific example of a nanofiltration-coupled electrodialysis apparatus for producing mineralized drinking water as described in Embodiment 1. It also serves to explain Embodiments 2 through 9. Specifically:

[0057] (1) Nanofiltration coupled with electrodialysis unit for mineralized drinking water production under normal operating conditions:

[0058] A device for producing mineralized drinking water by nanofiltration coupled with electrodialysis includes at least a nanofiltration unit, a first-stage reverse electrodialysis unit, a shore filtration-gravity flow ultrafiltration unit, and a second-stage reverse electrodialysis unit;

[0059] The pretreated influent I1, containing ions and potential organic pollutants, is introduced into the nanofiltration unit through the first inlet. The first freshwater L1 obtained by nanofiltration separation enters the first reverse electrodialysis unit through the first outlet and the second inlet. The first concentrate H1 produced by the nanofiltration unit enters the first reverse electrodialysis unit through the second outlet and the third inlet. The first freshwater L1 and the first concentrate H1 introduced into the first reverse electrodialysis unit undergo ion redistribution. The TDS of the freshwater is monitored using real-time water quality monitoring equipment and PLC control equipment, and the TDS of the effluent is controlled within the range of 120-200 mg / L. The effluent E1 obtained after ion distribution flows out of the system through the third outlet 23. The redistributed second concentrate H2 enters the second reverse electrodialysis unit through the fourth outlet and the fifth inlet, and undergoes ion distribution with the second river water R2 treated by the bank filtration-gravity flow ultrafiltration system. The resulting second effluent E2 flows out of the second reverse electrodialysis unit. The third concentrate H3 obtained after distribution flows back to the nanofiltration unit through the seventh outlet 44 and the first inlet 11.

[0060] The influent conditions are as follows: the influent is free from micro-pollutants, algae, emerging pollutants, and other organic pollutants that contaminate the water quality; the TDS concentration of the concentrate produced by the nanofiltration unit is higher than 1000 mg / L; the permanganate index is lower than 6 mg / L; and no perfluorinated compounds are detected in the raw water.

[0061] Under normal operating conditions, the membrane cleaning process of the reverse electrodialysis unit is as follows: the polarity of the first and second reverse electrodialysis units is reversed. After running for a certain period of time, based on the voltage generated by the reverse electrodialysis unit, when the voltage drops by 20%, a reverse voltage is applied to reduce colloidal and particulate matter pollution and assist in cleaning the ion exchange membrane.

[0062] In this embodiment, the first inlet is the inlet of the nanofiltration unit, the second inlet is the inlet of the first reverse electrodialysis unit, the third inlet is the inlet of the concentrate treatment unit, the fifth inlet is the inlet of the second reverse electrodialysis unit, the first outlet and the second outlet are the outlets of the nanofiltration unit, the third outlet and the fourth outlet are the outlets of the first reverse electrodialysis unit, and the seventh outlet is the outlet of the second reverse electrodialysis unit.

[0063] (2) Nanofiltration coupled electrodialysis unit for mineralized drinking water production under unconventional operating conditions with excessive organic matter.

[0064] Combination Figure 2 This implementation plan describes a device for producing mineralized drinking water using nanofiltration coupled with electrodialysis, which includes: a nanofiltration unit, a primary reverse electrodialysis unit, a shore filtration-gravity flow ultrafiltration unit, a secondary reverse electrodialysis unit, and a concentrate treatment unit.

[0065] Pretreated influent I1, containing ions and potential organic pollutants, is introduced into the nanofiltration unit through the first inlet. The first freshwater L1 obtained after nanofiltration separation enters the first reverse electrodialysis unit through the first outlet and second inlet. The first concentrate H1 produced by the nanofiltration unit enters the concentrate treatment unit for treatment through the second outlet and third inlet. The treated first concentrate H1 then enters the first reverse electrodialysis unit. Ion redistribution is performed on the first freshwater L1 and the first concentrate H1 introduced from the first reverse electrodialysis unit. Real-time water quality monitoring equipment and PLC control equipment are used to monitor the total dissolved solids (TDS) of the freshwater, controlling the effluent TDS within the range of 120-200 mg / L. The effluent E1 obtained after ion distribution exits the system through the third outlet. The redistributed second concentrate H2 enters the second reverse electrodialysis unit through the fourth outlet and fifth inlet, where it undergoes ion distribution with the second river water R2 treated by the bank filtration-gravity flow ultrafiltration system. The resulting second effluent E2 exits the system. The third concentrate H3 obtained after distribution is returned to the nanofiltration unit through the seventh outlet and first inlet.

[0066] The influent conditions are as follows: the influent contains micro-pollutants, algae, emerging pollutants, and other organic pollutants that contaminate the water quality; the TDS concentration of the concentrate produced by the nanofiltration system is higher than 1000 mg / L; the permanganate index is higher than 6 mg / L; and no perfluorinated compounds are detected in the raw water.

[0067] The concentrated wastewater treatment unit employs advanced oxidation treatment methods, using oxidants such as ozone and sodium hypochlorite. The ozone dosage is 0.8-2 times CODMn, and the sodium hypochlorite dosage is 0.8-1.5 times CODMn.

[0068] Cleaning process of reverse electrodialysis unit membrane under unconventional operating conditions: The polarity of the first and second reverse electrodialysis units is reversed. After running for a certain period of time, based on the voltage generated by the reverse electrodialysis unit, a reverse voltage is applied when the voltage drops by 20% to reduce colloidal and particulate matter pollution and assist in cleaning the ion exchange membrane.

[0069] (3) Nanofiltration coupled electrodialysis unit for the production of mineralized drinking water under unconventional operating conditions for detecting perfluorinated compounds

[0070] Pretreated influent I1, containing ions and potential organic pollutants, is introduced into the nanofiltration unit through the first inlet. The first freshwater L1 obtained after nanofiltration separation enters the first reverse electrodialysis unit through the first outlet and second inlet. The first concentrate H1 produced by the nanofiltration unit enters the concentrate treatment unit for treatment through the second outlet and third inlet. The treated first concentrate H1 then enters the first reverse electrodialysis unit. Ion redistribution is performed on the first freshwater L1 and the first concentrate H1 introduced from the first reverse electrodialysis unit. Real-time water quality monitoring equipment and PLC control equipment are used to monitor the total dissolved solids (TDS) of the freshwater, controlling the effluent TDS within the range of 120-200 mg / L. The effluent E1 obtained after ion distribution exits the system through the third outlet. The redistributed second concentrate H2 enters the second reverse electrodialysis unit through the fourth outlet and fifth inlet, where it undergoes ion distribution with the second river water R2 treated by the bank filtration-gravity flow ultrafiltration system. The resulting second effluent E2 exits the system. The third concentrate H3 obtained after distribution is returned to the nanofiltration unit through the seventh outlet and first inlet.

[0071] The influent conditions are as follows: the influent is free from micro-pollutants, algae, emerging pollutants, and other organic pollutants that contaminate the water quality; the TDS concentration of the concentrate produced by the nanofiltration unit is higher than 1000 mg / L; the permanganate index is lower than 6 mg / L; and perfluorinated compounds are detected in the raw water.

[0072] The concentrated water treatment unit employs an advanced reduction treatment method, specifically UV-catalyzed sodium bisulfite reduction, with a dosage of 6000-10000 times the molar concentration of perfluorinated compounds.

[0073] Cleaning process of reverse electrodialysis unit membrane under unconventional operating conditions: The polarity of the first and second reverse electrodialysis units is reversed. After running for a certain period of time, based on the voltage generated by the reverse electrodialysis unit, a reverse voltage is applied when the voltage drops by 20% to reduce colloidal and particulate matter pollution and assist in cleaning the ion exchange membrane.

[0074] (4) Nanofiltration coupled electrodialysis unit is used for mineralized drinking water production under unconventional operating conditions with low TDS concentration in raw water.

[0075] Pretreated influent I1, containing ions and potential organic pollutants, is introduced into the nanofiltration unit through the first inlet. The first freshwater L1 obtained after nanofiltration separation enters the first reverse electrodialysis unit through the first outlet and second inlet. The first concentrate H1 produced by the nanofiltration unit enters the concentrate treatment unit for treatment through the second outlet and third inlet. The treated first concentrate H1 then enters the first reverse electrodialysis unit. Ion redistribution is performed on the first freshwater L1 and the first concentrate H1 introduced from the first reverse electrodialysis unit. Real-time water quality monitoring equipment and PLC control equipment are used to monitor the total dissolved solids (TDS) of the freshwater, controlling the effluent TDS within the range of 120-200 mg / L. The effluent E1 obtained after ion distribution exits the system through the third outlet. The redistributed second concentrate H2 enters the second reverse electrodialysis unit through the fourth outlet and fifth inlet, where it undergoes ion distribution with the second river water R2 treated by the bank filtration-gravity flow ultrafiltration system. The resulting second effluent E2 exits the system. The third concentrate H3 obtained after distribution is returned to the nanofiltration unit through the seventh outlet and first inlet.

[0076] The influent conditions are as follows: the influent is free from micro-pollutants, algae, emerging pollutants, and other organic pollutants that contaminate the water quality; the TDS concentration of the concentrate produced by the nanofiltration unit is less than 1000 mg / L; the permanganate index is less than 6 mg / L; and no perfluorinated compounds are detected in the raw water.

[0077] When the TDS of the concentrate is below 1000 mg / L, the first reverse electrodialysis unit applies an auxiliary voltage in the direction of the natural salinity gradient to enhance ion transport. The voltage level is 0-6 V per membrane pair.

[0078] Cleaning process of reverse electrodialysis unit membrane under unconventional operating conditions: The polarity of the first and second reverse electrodialysis units is reversed. After running for a certain period of time, based on the voltage generated by the reverse electrodialysis unit, a reverse voltage is applied when the voltage drops by 20% to reduce colloidal and particulate matter pollution and assist in cleaning the ion exchange membrane.

[0079] Although preferred embodiments of this disclosure have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this disclosure.

[0080] Obviously, those skilled in the art can make various modifications and variations to this disclosure without departing from its spirit and scope. Therefore, if such modifications and variations fall within the scope of the claims of this disclosure and their equivalents, this disclosure is also intended to include such modifications and variations.

Claims

1. An apparatus for producing mineralized drinking water using nanofiltration coupled with electrodialysis, characterized in that, The device includes: Nanofiltration unit, first reverse electrodialysis unit, shore filtration-gravity flow ultrafiltration unit and second reverse electrodialysis unit; The pretreated influent containing ions and potential organic pollutants is introduced into the nanofiltration unit through the inlet. The nanofiltration separates the first freshwater and the first concentrated water, which then enter the first reverse electrodialysis unit. The first reverse electrodialysis unit redistributes ions based on the introduced first freshwater and first concentrated water. Using real-time water quality monitoring equipment and PLC control equipment, the TDS of the freshwater is monitored, and the TDS of the effluent is controlled within the range of 120-200 mg / L. The effluent obtained after ion distribution exits the first reverse electrodialysis unit, and the redistributed second concentrated water enters the second reverse electrodialysis unit to undergo ion distribution with the second river water treated by the bank filtration-gravity flow ultrafiltration system. The resulting second effluent exits the second reverse electrodialysis unit, and the third concentrated water obtained after distribution is returned to the nanofiltration unit. Reverse electrodialysis unit membrane cleaning process: The polarity of the first reverse electrodialysis unit and the second reverse electrodialysis unit is reversed. After running for a certain period of time, the reverse voltage is applied based on the voltage generated by the reverse electrodialysis unit when the voltage drops by 20%. The influent conditions for the pretreated influent containing ions and potential organic pollutants are as follows: the influent contains micro-pollutants, algae, and emerging pollutants, and the TDS concentration of the concentrate produced by the nanofiltration unit is higher than 1000 mg / L, the permanganate index is higher than 6 mg / L, and no perfluorinated compounds are detected in the raw water. The device further includes a concentrate treatment unit, which is disposed between the nanofiltration unit and the first reverse electrodialysis unit. The concentrate treatment unit selects an advanced oxidation or advanced reduction treatment method according to the organic pollution problem of the influent water. Specifically, when the permanganate index exceeds the limit value, advanced oxidation treatment is selected, and when perfluorinated compounds are detected, advanced reduction treatment is selected.

2. The apparatus for producing mineralized drinking water by nanofiltration coupled with electrodialysis according to claim 1, characterized in that, The first reverse electrodialysis unit selects conventional reverse electrodialysis technology and assisted reverse electrodialysis technology according to the TDS level of the concentrate in the nanofiltration unit. When the TDS of the concentrate is less than 1000 mg / L, an auxiliary voltage is applied in the direction of the natural salinity gradient to enhance ion transport. The voltage level is 0~6V / membrane pair.

3. The apparatus for producing mineralized drinking water by nanofiltration coupled with electrodialysis according to claim 1, characterized in that, The processing parameters of the nanofiltration unit are as follows: operating pressure is 0.3-3 MPa, recovery rate is selected according to actual operating conditions as 70%-90%, influent turbidity of nanofiltration unit is less than 0.5 NTU, and pH is in the range of 6.8-7.

2.

4. The apparatus for producing mineralized drinking water by nanofiltration coupled with electrodialysis according to claim 1, characterized in that, The processing parameters of the first reverse electrodialysis unit are: the turbidity of the concentrate influent is less than 0.1 NTU, the TDS of the influent is less than 5000 mg / L, and the operating flow rate is controlled in the range of 5-30 cm / s.

5. The apparatus for producing mineralized drinking water by nanofiltration coupled with electrodialysis according to claim 1, characterized in that, The treatment parameters of the shore filter-gravity flow ultrafiltration unit are: effluent turbidity controlled within 0.2 NTU, and effluent TDS in the range of 10-1000 mg / L.

6. The apparatus for producing mineralized drinking water by nanofiltration coupled with electrodialysis according to claim 1, characterized in that, When the concentrated wastewater treatment unit selects advanced oxidation treatment, ozone or sodium hypochlorite is chosen, with the ozone dosage being 0.8-2 times the COD. Mn The dosage of sodium hypochlorite is 0.8-1.5 times the COD. Mn When selecting advanced reduction treatment, UV-catalyzed sodium bisulfite reduction is chosen, with an addition amount of 6000-10000 times the molar concentration of perfluorinated compounds.

7. A method for producing mineralized drinking water, characterized in that, The method is implemented based on the apparatus for producing mineralized drinking water by nanofiltration coupled with electrodialysis as described in any one of claims 1 to 6, and the method includes: The raw water is nano-filtered, and the fresh water and concentrated water enter the first reverse electrodialysis unit for ion separation to obtain mineralized effluent. The concentrated water enters the second reverse electrodialysis unit and undergoes ion separation again with the river water that has been treated by bank filtration-gravity flow ultrafiltration. The resulting concentrated effluent is returned to the nanofiltration inlet. The river water after ion separation is used for landscape water or fire fighting water.

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