Device and method for producing mineralized drinking water by coupling nanofiltration with electrodialysis

Abstract

The invention discloses a device and method for producing mineralized drinking water through nanofiltration coupled electrodialysis, and relates to the technical field of water treatment. The problems that a nanofiltration membrane can remove various natural mineral ions beneficial to human bodies while removing various pollutants, and the separation performance of the nanofiltration membrane is not enough to be matched with a separation target are solved. The device is characterized in that pretreated inlet water containing ions and potential organic pollutants is introduced into a nanofiltration unit through an inlet of the nanofiltration unit, first fresh water and first concentrated water are obtained through nanofiltration separation, and the first fresh water and the first concentrated water respectively enter a first reverse electrodialysis unit; the first reverse electrodialysis unit is used for ion redistribution; the redistributed second concentrated water enters a second-stage reverse electrodialysis unit, ion distribution is carried out on the redistributed second concentrated water and second inlet water treated by the shore filtration-gravity flow ultrafiltration system, obtained second effluent flows out of the second reverse electrodialysis unit, and third concentrated water obtained after distribution flows back to the nanofiltration unit. The method is applied to the field of drinking water production.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a device for producing mineralized drinking water by nanofiltration coupled electrodialysis. Background Art

[0002] In recent years, as people's requirements for drinking water quality continue to increase, 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 in water, but at the same time they will also remove some natural mineral ions that are beneficial to the human body, resulting in low mineral ion content in the produced water, which is not conducive to human health. To solve this problem, people have proposed solutions such as developing new nanofiltration membrane materials or adding mineralized filter elements, but the research and development cycle of new membrane materials is long and the cost is high, and the mineral types in the mineralized filter element are single and artificial minerals, and their safety and health need further research.

[0003] The mineral ion concentration in the nanofiltration concentrate produced during the nanofiltration process is high, and the source is more natural and reliable, which is expected to become a reliable source of ion supplement for nanofiltration effluent. However, the existing technology cannot efficiently separate and controllably add mineral ions in nanofiltration concentrate, making it difficult to meet the needs of residents for high-quality drinking water. Therefore, it is urgent to develop a new water treatment technology that can achieve efficient separation of organic matter and mineral ions and controllably add mineral ions to produce mineralized drinking water with a moderate mineral content.

[0004] There are currently some invention patents to solve the problem that nanofiltration membranes not only remove a variety of pollutants, but also remove a variety of natural mineral ions that are beneficial to the human body, and the separation performance of nanofiltration membranes is not well matched with the separation target. For example:

[0005] CN114929370A discloses a method for providing purified and mineralized drinking water from contaminated fresh water or brackish water. The patent uses a reverse electrodialysis unit and an auxiliary reverse electrodialysis unit to distribute ions in nanofiltration concentrated water to achieve controllable addition of mineral ions. However, the patent still has the problem 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, removes trace organic matter harmful to the human body, and retains most of the inorganic salts. However, the patent still has the problem of using low desalination membrane elements and filters to remove pollution in water, and the ability to selectively remove toxic and harmful ions is weak. Summary of the invention

[0007] The present invention aims at the problem that nanofiltration membrane removes a variety of pollutants while also removing a variety of natural mineral ions that are beneficial to the human body, and the separation performance of the nanofiltration membrane is not sufficiently matched with the separation target. A device for producing mineralized drinking water by nanofiltration coupling electrodialysis is proposed, and the device comprises:

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

[0009] The pretreated influent containing ions and potential organic pollutants is introduced into the nanofiltration unit through the inlet of the nanofiltration unit, and the first fresh water and the first concentrated water are obtained by nanofiltration separation. The first fresh water and the first concentrated water enter the first reverse electrodialysis unit respectively; the first reverse electrodialysis unit redistributes ions according to the introduced first fresh water and the first concentrated water, and uses real-time water quality monitoring equipment and PLC control equipment to monitor the fresh water TDS, and control the effluent TDS within the range of 120-200 mg / L; the effluent obtained after ion distribution flows out of the first reverse electrodialysis unit, and the second concentrated water after redistribution enters the secondary reverse electrodialysis unit, and performs ion distribution with the second river water treated by the shore filtration-gravity flow ultrafiltration system. The second effluent obtained flows out of the second reverse electrodialysis unit, and the third concentrated water obtained after distribution flows back to the nanofiltration unit.

[0010] Furthermore, a preferred method is proposed, in which the water quality conditions of the influent containing ions and potential organic pollutants after pretreatment are: the influent has problems with micropollutants, algae, and emerging pollutants, and the TDS concentration of the concentrated water 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 comprises: a concentrate treatment unit, wherein the concentrate treatment unit is arranged between the nanofiltration unit and the first reverse electrodialysis unit, and wherein the concentrate treatment unit selects advanced oxidation or advanced reduction treatment means according to the water quality problem of organic pollution of the influent water, wherein when the permanganate index exceeds the limit value, advanced oxidation treatment is selected, and when excessive perfluorinated compounds are detected, advanced reduction treatment means is selected.

[0012] Furthermore, a preferred embodiment is proposed, wherein 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 is reduced by 20%.

[0013] Furthermore, a preferred method is proposed, in which the first reverse electrodialysis unit selects conventional reverse electrodialysis technology and auxiliary 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, and the voltage level is 0 to 6 V / pair of membranes.

[0014] Furthermore, a preferred method is proposed, in which the processing parameters of the nanofiltration unit are: operating pressure is 0.3-3MPa, the recovery rate is selected to be 70%-90% based on the actual operating conditions, the turbidity of the nanofiltration unit inlet water is lower than 0.5NTU, and the pH is in the range of 6.8 to 7.2.

[0015] Furthermore, a preferred embodiment is proposed, wherein the processing parameters of the first reverse electrodialysis unit are: the concentrated water inlet turbidity is lower than 0.1 NTU, the inlet TDS is lower 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, in which the treatment parameters of the shore filtration-gravity flow ultrafiltration unit are: the effluent turbidity is controlled within 0.2NTU, and the effluent TDS is in the range of 10-1000mg / L.

[0017] Furthermore, a preferred method is proposed, 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 COD Mn , the dosage of sodium hypochlorite is 0.8-1.5 times COD Mn When advanced reduction treatment is selected, UV-catalyzed sodium bisulfite reduction is selected, and the dosage is 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, which is implemented based on a device for producing mineralized drinking water by nanofiltration coupled electrodialysis as described in any one of the above items, and the method comprises:

[0019] The raw water is nanofiltered, and the fresh water and concentrated water enter the first reverse electrodialysis unit for ion distribution to obtain mineralized effluent. The concentrated water enters the second reverse electrodialysis unit for ion distribution again with the river water treated by shore filtration-gravity flow ultrafiltration. The concentrated effluent obtained is returned to the nanofiltration inlet. After ion distribution, the river water is used for landscape water or fire fighting water.

[0020] The present invention is beneficial in that:

[0021] 1. The present invention organically couples nanofiltration technology with reverse electrodialysis technology. This coupling method gives full play to the advantages of the two technologies, overcomes the limitations of traditional single technology in mineralization and water quality control, and provides an innovative solution for the production of mineralized drinking water;

[0022] 2. In the whole production process of the present invention, the source of mineral ions is endogenous ions in the source water, which reduces the use of chemical agents and the impact on the environment. The concentrated brine produced by the system is reasonably treated and recycled to maximize the utilization of ion resources, which is in line with the concept of sustainable development;

[0023] 3. Compared with the traditional mineralized water production method, the present invention has lower energy consumption. The synergistic effect of nanofiltration and reverse electrodialysis process reduces energy costs;

[0024] 4. The present invention can achieve efficient separation of organic matter and mineral ions, and can add mineral ions in a controllable manner, thereby producing mineralized drinking water with a moderate mineral content to meet the needs of residents for high-quality drinking water;

[0025] 5. The present invention utilizes mineral ions from natural sources in nanofiltration concentrated water as an ion supplement source, without the need to develop new nanofiltration membrane materials or add mineralized filter elements, thus avoiding high R&D costs and safety and health issues of artificial minerals;

[0026] 6. The present invention adopts multi-stage electrodialysis ion distribution technology, which can make full use of the mineral ion resources in nanofiltration concentrated water and river water, improve ion utilization rate 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 a high processing efficiency;

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

[0029] The invention is applied to the field of drinking water production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart of the nanofiltration-coupled electrodialysis device described in Embodiment 1 used for producing mineralized drinking water under normal operating conditions;

[0031] Figure 2 This is a flow chart of the nanofiltration-coupled electrodialysis device described in Embodiment 11 for producing 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 Implementation Example 11. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0034] Implementation method 1, see Figure 1 The present embodiment is described as follows. The device for producing mineralized drinking water by nanofiltration coupled with electrodialysis in the present embodiment comprises:

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

[0036] The pretreated influent containing ions and potential organic pollutants is introduced into the nanofiltration unit through the inlet of the nanofiltration unit, and the first fresh water and the first concentrated water are obtained by nanofiltration separation. The first fresh water and the first concentrated water enter the first reverse electrodialysis unit respectively; the first reverse electrodialysis unit redistributes ions according to the introduced first fresh water and the first concentrated water, and uses real-time water quality monitoring equipment and PLC control equipment to monitor the fresh water TDS, and control the effluent TDS within the range of 120-200 mg / L; the effluent obtained after ion distribution flows out of the first reverse electrodialysis unit, and the second concentrated water after redistribution enters the secondary reverse electrodialysis unit, and performs ion distribution with the second river water treated by the shore filtration-gravity flow ultrafiltration system. The second effluent obtained flows out of the second reverse electrodialysis unit, and the third concentrated water obtained after distribution flows back to the nanofiltration unit.

[0037] In practical applications, the number and stages of nanofiltration unit membrane components are determined according to the processing scale and recovery rate, and the number of membrane stack ion exchange membrane pairs in the first reverse electrodialysis unit and the second reverse electrodialysis unit is 10 to 500 pairs depending on the unit size.

[0038] In this embodiment, by introducing a reverse electrodialysis unit, it is possible to achieve the regulation and addition of mineral ions in water. In particular, in the combined application of the first reverse electrodialysis unit and the second reverse electrodialysis unit, the concentration of mineral ions in water can be accurately adjusted as needed, so that the purified water not only removes harmful pollutants, but also retains and regulates beneficial mineral components (such as calcium, magnesium, etc.). This avoids the problem of loss of beneficial mineral ions commonly seen in traditional nanofiltration membrane technology.

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

[0040] The device combines a multi-stage reverse electrodialysis unit with a shore filtration-gravity flow ultrafiltration system, which not only improves the quality and safety of water, but also optimizes the mineral ion content in the water during the multi-stage distribution process. In each reverse electrodialysis unit, the water flow undergoes multiple ion redistribution, which can remove harmful ions while retaining the required beneficial mineral ions, further improving the water quality.

[0041] Embodiment 2. This embodiment is a further limitation of the device for producing mineralized drinking water by nanofiltration coupled electrodialysis described in Embodiment 1. The water quality conditions of the pretreated influent containing ions and potential organic pollutants are as follows: the influent contains micropollutants, algae, and emerging pollutants, and the TDS concentration of the concentrated water 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] Embodiment 3. This embodiment is a further limitation of the device for producing mineralized drinking water by nanofiltration-coupled electrodialysis as described in embodiment 1. The device also includes: a concentrate treatment unit, which is arranged between the nanofiltration unit and the first reverse electrodialysis unit. The concentrate treatment unit selects advanced oxidation or advanced reduction treatment methods according to the water quality problem of organic pollution in the influent. When the permanganate index exceeds the limit value, advanced oxidation treatment is selected, and when excessive perfluorinated compounds are detected, advanced reduction treatment methods are selected.

[0043] In this embodiment, by introducing a concentrated water treatment unit, the device can carry out targeted treatment according to the characteristics of different pollutants in the water (such as organic pollutants, permanganate index and perfluorinated compounds, etc.). This flexible treatment method can ensure the efficient removal of various pollutants during the water purification process: for water sources with a high permanganate index, organic pollutants in the water can be oxidized by the action of strong oxidants, reducing the concentration of organic pollutants and ensuring safer water quality. For water sources containing perfluorinated compounds, the use of advanced reduction treatment methods can effectively decompose these harmful substances and prevent them from posing a potential threat to human health.

[0044] The introduction of the concentrated water treatment unit makes water treatment more refined. When there are different types of pollutants in the incoming water, the traditional single water treatment method may be difficult to deal with effectively, but the device can select different treatment methods according to the specific type of pollutants. Through this flexible choice, harmful substances in the water can be efficiently removed to ensure that the water quality meets the drinking standard.

[0045] Embodiment 4. This embodiment further limits the device for producing mineralized drinking water by nanofiltration coupled electrodialysis as described in embodiment 1, wherein 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 is reduced by 20%.

[0046] Embodiment 5. This embodiment is a further limitation of the device for producing mineralized drinking water by nanofiltration-coupled electrodialysis as described in Embodiment 4. The first reverse electrodialysis unit selects conventional reverse electrodialysis technology and auxiliary reverse electrodialysis technology according to the TDS level of concentrate in the nanofiltration unit. When the TDS of 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 / pair of membrane pairs.

[0047] Combined with the fourth embodiment, this embodiment is explained. By adjusting the electrode polarity of the reverse electrodialysis unit and applying a reverse voltage when the voltage is reduced by 20%, it is helpful to optimize the ion migration during the electrodialysis process, reduce ion accumulation and improve efficiency. This design of polarity reversal and voltage change ensures that the current and ion transmission during the electrodialysis process are more efficient, especially when the concentrated water TDS is low, it can enhance ion transmission and improve the quality of mineralized water. When the concentrated water TDS is lower than 1000 mg / L, the auxiliary reverse electrodialysis technology is used to apply an auxiliary voltage (0-6V / pair of membrane pairs) in the direction of the natural salinity gradient to enhance the ion transmission capacity of the low TDS water source. This strategy is very effective when the water quality is soft and the mineralization is low, and can further improve the mineralization degree and taste of mineralized drinking water. The combination of nanofiltration and reverse electrodialysis can accurately control the mineral content in the water and provide drinking water with a moderate mineralization level. Through the optimized design of the reverse electrodialysis unit, ion transmission can be further enhanced, so that the water quality maintains an appropriate mineral concentration without sacrificing health standards. The application of reverse electrodialysis allows unnecessary ions in water to be effectively removed while replenishing necessary minerals, thereby improving the taste and health of the water.

[0048] Implementation method six. This implementation method is a further limitation of the device for producing mineralized drinking water by nanofiltration coupled electrodialysis described in implementation method one. The processing parameters of the nanofiltration unit are: operating pressure of 0.3-3MPa, recovery rate of 70%-90% is selected according to actual operating conditions, turbidity of inlet water of the nanofiltration unit is lower than 0.5NTU, and pH is in the range of 6.8 to 7.2.

[0049] Embodiment 7. This embodiment further limits the device for producing mineralized drinking water by nanofiltration-coupled electrodialysis described in embodiment 1. The processing parameters of the first reverse electrodialysis unit are: the turbidity of the concentrated water is lower than 0.1NTU, the inlet TDS is lower than 5000mg / L, and the operating flow rate is controlled in the range of 5-30cm / s.

[0050] Embodiment 8. This embodiment further limits the device for producing mineralized drinking water by nanofiltration coupled electrodialysis as described in Embodiment 1. The processing parameters of the shore filtration-gravity flow ultrafiltration unit are as follows: the effluent turbidity is controlled within 0.2NTU, and the effluent TDS is in the range of 10-1000mg / L.

[0051] Combined with the sixth and seventh embodiments, this embodiment is explained. The turbidity of the inlet water of the nanofiltration unit is lower than 0.5NTU, which ensures that the inlet water quality is good, avoids the contamination of the membrane by particulate matter and suspended matter, can effectively remove most of the soluble solids (TDS) and certain harmful substances (such as heavy metals, bacteria, etc.) in the water, and improves the safety of drinking water. The reverse electrodialysis unit controls the turbidity of the concentrated water inlet to below 0.1NTU, and the TDS is lower than 5000mg / L, which helps to further reduce the high concentration of dissolved substances in the water and achieve the balance of salt and minerals required for mineralized water. The pH range of the nanofiltration unit is controlled at 6.8-7.2 to ensure the stability of the pH of the water and avoid the potential harm of over-acidic or over-alkaline water to human health. This range is suitable for the standard of human drinking water, and can also ensure the normal operation of the equipment. The recovery rate of the nanofiltration unit is 70%-90%. By optimizing the operation, it can reduce water waste, improve water utilization, and ensure production efficiency and water quality stability.

[0052] The device can effectively remove harmful substances in the water and retain appropriate minerals and salts through a combination of nanofiltration and electrodialysis. The final effluent TDS is controlled within the range of 10-1000mg / L, which meets the standards of mineralized water. It not only retains the beneficial minerals in the water, but also avoids health problems caused by excessive or low salt levels in the water. The effluent turbidity of the shore filtration-gravity flow ultrafiltration unit is controlled within 0.2NTU, which helps to further improve the transparency and clarity of the water and provide better quality drinking water.

[0053] Embodiment 9. This embodiment is a further limitation of the device for producing mineralized drinking water by nanofiltration coupled electrodialysis as described in Embodiment 3. 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 of COD Mn , the dosage of sodium hypochlorite is 0.8-1.5 times COD Mn When advanced reduction treatment is selected, UV-catalyzed sodium bisulfite reduction is selected, and the dosage is 6000-10000 times the molar concentration of perfluorinated compounds.

[0054] Embodiment 10: A method for producing mineralized drinking water according to this embodiment, the method is implemented based on a device for producing mineralized drinking water by nanofiltration coupled electrodialysis according to any one of embodiments 1 to 9, and the method comprises:

[0055] The raw water is nanofiltered, and the fresh water and concentrated water enter the first reverse electrodialysis unit for ion distribution to obtain mineralized effluent. The concentrated water enters the second reverse electrodialysis unit for ion distribution again with the river water treated by shore filtration-gravity flow ultrafiltration. The concentrated effluent obtained is returned to the nanofiltration inlet. After ion distribution, the river water is used for landscape water or fire fighting water.

[0056] Implementation Method 11: See Figure 2 and Figure 3 This embodiment provides a specific example of the device for producing mineralized drinking water by nanofiltration coupled with electrodialysis as described in the first embodiment, and is also used to explain the second to ninth embodiments, specifically:

[0057] (1) Nanofiltration coupled electrodialysis device is used for the production of mineralized drinking water under normal operating conditions:

[0058] The device for producing mineralized drinking water by nanofiltration coupled electrodialysis comprises at least a nanofiltration unit, a primary reverse electrodialysis unit, a shore filtration-gravity flow ultrafiltration unit and a secondary reverse electrodialysis unit;

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

[0060] The water inlet conditions are: the inlet water does not contain water quality problems caused by micropollutants, algae, emerging pollutants and other organic pollutants, and the TDS concentration of the concentrated water 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] Reverse electrodialysis unit membrane cleaning process under normal operating conditions: the polarity of the first reverse electrodialysis unit and the second reverse electrodialysis unit are reversed. After running for a certain period of time, the reverse electrodialysis unit power generation voltage is used as the basis. When the voltage drops by 20%, the reverse voltage is applied to reduce colloid and particulate pollution and assist in cleaning the ion exchange membrane.

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

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

[0064] Combination Figure 2 To illustrate this embodiment, the device for producing mineralized drinking water by nanofiltration coupled electrodialysis includes: a nanofiltration unit, a primary reverse electrodialysis unit, a shore filtration-gravity flow ultrafiltration unit, a secondary reverse electrodialysis unit and a concentrated water treatment unit.

[0065] The pre-treated influent I1 containing ions and potential organic pollutants is introduced into the nanofiltration unit through the first inlet, the first fresh water L1 obtained by nanofiltration separation enters the first reverse electrodialysis unit through the first outlet and the second inlet, the first concentrated water H1 produced by the nanofiltration unit enters the concentrated water treatment unit for treatment through the second outlet and the third inlet, and the treated first concentrated water H1 enters the first reverse electrodialysis unit. After the first fresh water L1 and the first concentrated water H1 introduced into the first reverse electrodialysis unit are subjected to ion redistribution, the total dissolved solids TDS of the fresh water is monitored by real-time water quality monitoring equipment and PLC control equipment, and the effluent TDS is controlled within the range of 120-200 mg / L. After ion distribution, the effluent E1 is obtained through the third outlet (outflow system, the redistributed second concentrated water H2 enters the second reverse electrodialysis unit through the fourth outlet and the fifth inlet, and ion distribution is performed with the second river water R2 treated by the bank filtration-gravity flow ultrafiltration system. The obtained second effluent E2 flows out of the system, and the third concentrated water H3 obtained after distribution flows back to the nanofiltration unit through the seventh outlet and the first inlet.

[0066] The water inlet conditions are: the water quality is polluted by micropollutants, algae, emerging pollutants and other organic matter, and the TDS concentration of the concentrated water 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 water treatment unit selects advanced oxidation treatment means, selects 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] Reverse electrodialysis unit membrane cleaning process under unconventional operating conditions: the polarity of the first reverse electrodialysis unit and the second reverse electrodialysis unit are reversed, and after a certain period of operation, the reverse electrodialysis unit power generation voltage is used as the basis. When the voltage drops by 20%, a reverse voltage is applied to reduce colloid and particulate pollution and assist in cleaning the ion exchange membrane.

[0069] (3) Nanofiltration coupled electrodialysis device for the production of mineralized drinking water under unconventional operating conditions where perfluorinated compounds were detected

[0070] The pre-treated influent I1 containing ions and potential organic pollutants is introduced into the nanofiltration unit through the first inlet, the first fresh water L1 obtained by nanofiltration separation enters the first reverse electrodialysis unit through the first outlet and the second inlet, the first concentrated water H1 produced by the nanofiltration unit enters the concentrated water treatment unit for treatment through the second outlet and the third inlet, and the treated first concentrated water H1 enters the first reverse electrodialysis unit. After the first fresh water L1 and the first concentrated water H1 introduced into the first reverse electrodialysis unit are subjected to ion redistribution, the total dissolved solids TDS of the fresh water is monitored by real-time water quality monitoring equipment and PLC control equipment, and the effluent TDS is controlled within the range of 120-200 mg / L. After ion distribution, the effluent E1 is obtained through the third outlet (outflow system, the redistributed second concentrated water H2 enters the second reverse electrodialysis unit through the fourth outlet and the fifth inlet, and ion distribution is performed with the second river water R2 treated by the bank filtration-gravity flow ultrafiltration system. The obtained second effluent E2 flows out of the system, and the third concentrated water H3 obtained after distribution flows back to the nanofiltration unit through the seventh outlet and the first inlet.

[0071] The water inlet conditions are: there are no water quality problems caused by inlet organic matter such as micropollutants, algae, and emerging pollutants, and the TDS concentration of the concentrated water 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 selects an advanced reduction treatment method, selects UV catalytic sodium bisulfite reduction, and the dosage is 6000-10000 times the molar concentration of the perfluorinated compound.

[0073] Reverse electrodialysis unit membrane cleaning process under unconventional operating conditions: the polarity of the first reverse electrodialysis unit and the second reverse electrodialysis unit are reversed, and after a certain period of operation, the reverse electrodialysis unit power generation voltage is used as the basis. When the voltage drops by 20%, a reverse voltage is applied to reduce colloid and particulate pollution and assist in cleaning the ion exchange membrane.

[0074] (4) Nanofiltration coupled electrodialysis device for the production of mineralized drinking water under unconventional operating conditions with low raw water TDS concentration

[0075] The pre-treated influent I1 containing ions and potential organic pollutants is introduced into the nanofiltration unit through the first inlet, the first fresh water L1 obtained by nanofiltration separation enters the first reverse electrodialysis unit through the first outlet and the second inlet, the first concentrated water H1 produced by the nanofiltration unit enters the concentrated water treatment unit for treatment through the second outlet and the third inlet, and the treated first concentrated water H1 enters the first reverse electrodialysis unit. After the first fresh water L1 and the first concentrated water H1 introduced into the first reverse electrodialysis unit are subjected to ion redistribution, the total dissolved solids TDS of the fresh water is monitored by real-time water quality monitoring equipment and PLC control equipment, and the effluent TDS is controlled within the range of 120-200 mg / L. After ion distribution, the effluent E1 is obtained through the third outlet (outflow system, the redistributed second concentrated water H2 enters the second reverse electrodialysis unit through the fourth outlet and the fifth inlet, and ion distribution is performed with the second river water R2 treated by the bank filtration-gravity flow ultrafiltration system. The obtained second effluent E2 flows out of the system, and the third concentrated water H3 obtained after distribution flows back to the nanofiltration unit through the seventh outlet and the first inlet.

[0076] The water inlet conditions are: there are no water quality problems caused by inlet organic matter such as micropollutants, algae, and emerging pollutants, and the TDS concentration of the concentrated water produced by the nanofiltration unit is lower than 1000 mg / L, the permanganate index is lower than 6 mg / L, and no perfluorinated compounds are detected in the raw water.

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

[0078] Reverse electrodialysis unit membrane cleaning process under unconventional operating conditions: the polarity of the first reverse electrodialysis unit and the second reverse electrodialysis unit are reversed, and after a certain period of operation, the reverse electrodialysis unit power generation voltage is used as the basis. When the voltage drops by 20%, a reverse voltage is applied to reduce colloid and particulate pollution and assist in cleaning the ion exchange membrane.

[0079] Although the preferred embodiments of the present disclosure have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present disclosure.

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

Claims

1. A device for producing mineralized drinking water by nanofiltration coupled electrodialysis, characterized in that: The device comprises: a nanofiltration unit, a first reverse electrodialysis unit, a shore filtration-gravity flow ultrafiltration unit, and a second reverse electrodialysis unit; The pretreated influent containing ions and potential organic pollutants is introduced into the nanofiltration unit through the inlet of the nanofiltration unit, and the first fresh water and the first concentrated water are obtained by nanofiltration separation. The first fresh water and the first concentrated water enter the first reverse electrodialysis unit respectively; the first reverse electrodialysis unit redistributes ions according to the introduced first fresh water and the first concentrated water, and uses real-time water quality monitoring equipment and PLC control equipment to monitor the fresh water TDS, and control the effluent TDS within the range of 120-200 mg / L; the effluent obtained after ion distribution flows out of the first reverse electrodialysis unit, and the second concentrated water after redistribution enters the secondary reverse electrodialysis unit, and performs ion distribution with the second river water treated by the shore filtration-gravity flow ultrafiltration system. The second effluent obtained flows out of the second reverse electrodialysis unit, and the third concentrated water obtained after distribution flows back to the nanofiltration unit.

2. The device for producing mineralized drinking water by nanofiltration coupled electrodialysis according to claim 1, characterized in that: The inlet conditions of the pretreated influent containing ions and potential organic pollutants are as follows: the influent contains micropollutants, algae, and emerging pollutants, and the TDS concentration of the concentrated water 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.

3. The device for producing mineralized drinking water by nanofiltration coupled electrodialysis according to claim 1, characterized in that: The device also includes: a concentrated water treatment unit, which is arranged between the nanofiltration unit and the first reverse electrodialysis unit. The concentrated water treatment unit selects advanced oxidation or advanced reduction treatment methods according to the water quality problem of organic pollution in the influent, wherein when the permanganate index exceeds the limit value, the advanced oxidation treatment is selected, and when perfluorinated compounds are detected, the advanced reduction treatment method is selected.

4. The device for producing mineralized drinking water by nanofiltration coupled electrodialysis according to claim 1, characterized in that: 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 is reduced by 20%.

5. The device for producing mineralized drinking water by nanofiltration coupled electrodialysis according to claim 4, characterized in that: The first reverse electrodialysis unit selects conventional reverse electrodialysis technology and auxiliary 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.

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

2.

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

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

9. The device for producing mineralized drinking water by nanofiltration coupled electrodialysis according to claim 3, characterized in that: 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 COD Mn , the dosage of sodium hypochlorite is 0.8-1.5 times COD Mn When advanced reduction treatment is selected, UV-catalyzed sodium bisulfite reduction is selected, and the dosage is 6000-10000 times the molar concentration of perfluorinated compounds.

10. A method for producing mineralized drinking water, characterized in that: The method is implemented based on the device for producing mineralized drinking water by nanofiltration coupled electrodialysis according to any one of claims 1 to 9, and the method comprises: The raw water is nanofiltered, and the fresh water and concentrated water enter the first reverse electrodialysis unit for ion distribution to obtain mineralized effluent. The concentrated water enters the second reverse electrodialysis unit for ion distribution again with the river water treated by shore filtration-gravity flow ultrafiltration. The concentrated effluent obtained is returned to the nanofiltration inlet. After ion distribution, the river water is used for landscape water or fire fighting water.

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