An ultraviolet-nanofiltration coupled water purification system

Abstract

The application discloses a kind of ultraviolet-nanofiltration coupling water purification systems, it is related to water treatment technical field, solve the biological pollution of drinking water nanofiltration process nanofiltration membrane and the single function of ultraviolet alone use Problem.The raw water is sent into ultraviolet-nanofiltration coupling device after pretreatment and once dosing filtration;Ultraviolet emission device in ultraviolet-nanofiltration coupling device emits ultraviolet rays to disinfect membrane element;The concentrated water generated by ultraviolet-nanofiltration coupling device removes sediment and is filtered into roll type nanofiltration membrane device to carry out secondary concentration separation, and the concentrated water separated out enters into the photocatalytic pool of pollutant treatment system and removes pollutants by the combined action of reagent and ultraviolet rays.The application couples ultraviolet emission device into drinking water nanofiltration device, avoids the biological pollution of nanofiltration membrane, strengthens catalytic oxidation-reduction effect, sets up ultraviolet emission device in photocatalytic pool, respectively improves catalytic reduction and catalytic oxidation effect, reaches the goal of nanofiltration concentrated water near zero discharge.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, in particular to an ultraviolet-nanofiltration coupled water purification system. Background Art

[0002] Nanofiltration is a membrane separation technology between ultrafiltration and reverse osmosis. It features high separation efficiency and selective separation, and has been widely used in a variety of fields, including drinking water purification, wastewater reuse, and food processing. In drinking water treatment in particular, nanofiltration membranes can effectively remove large organic molecules and some inorganic ions from water, making it one of the key technologies for high-quality water treatment. However, nanofiltration faces some limitations in its application, especially the problem of biological contamination on the surface of nanofiltration membranes. This requires additional raw water disinfection equipment and reducing agent dosing equipment for the nanofiltration process, which requires high control accuracy and increases the complexity of the system. In addition, the concentrated water produced by the nanofiltration process contains a high concentration of organic pollutants. How to efficiently treat the concentrated water to reduce environmental pollution and achieve resource recovery is an important issue currently faced.

[0003] In nanofiltration processes, pretreatment units typically use chlorine disinfection to inactivate microorganisms and prevent biofouling. However, the presence of chlorine can damage the nanofiltration membrane through oxidation, so the effluent from the pretreatment unit must be dechlorinated before entering the membrane element. In the absence of biocides such as residual chlorine in the membrane element, microbial contamination may occur on the nanofiltration membrane surface. This phenomenon shortens the life of the nanofiltration membrane, affects the membrane's retention function, and makes it impossible to ensure the safety of the produced water for drinking. Controlling membrane surface biofouling has become a bottleneck in nanofiltration applications.

[0004] Through the membrane retention function, the pre-membrane brine produced by the nanofiltration process usually contains natural organic matter such as humic acid and microbial dissolved organic matter, new pollutants such as antibiotics and per- and polyfluoroalkyl substances (PFAS), and trace organic pollutants such as chloroform and its intermediates. Brine treatment faces problems such as complex water quality components and low biodegradability. Currently, common brine treatment and disposal methods include entering the sewage treatment system, brine re-injection, ozone oxidation, and advanced oxidation processes combined with ozone. However, these methods still have many problems in practical applications, such as the increased environmental burden caused by brine re-injection, high oxidant dosage but poor effect, and low water recovery rate. The process concept often adopts a superposition method, which has low treatment efficiency. It is necessary to improve the water recovery rate of the brine treatment process through process innovation, thereby reducing the dosage of chemicals.

[0005] Ultraviolet disinfection is a physical disinfection method that does not introduce chemical agents and has no secondary pollution. It can kill bacteria and viruses in water in a short time and is not affected by fluctuations in water quality. At the same time, ultraviolet rays can effectively decompose organic pollutants in water through catalytic oxidation and reduction reactions. Therefore, ultraviolet technology has the potential to solve the problems of disinfection and concentrated water treatment at the same time. However, most of the ultraviolet equipment on the current market is used in combination with nanofiltration equipment as an independent unit, and usually uses centimeter-level diameter lamps, and mainly focuses on the disinfection function, making it difficult to achieve the coupled application of multiple functions in one system. The existing technology still lacks a coupled process that can realize the coordinated application of disinfection, photocatalytic oxidation and photocatalytic reduction in one system. Summary of the Invention

[0006] To address the aforementioned issues of biological contamination of nanofiltration membranes in existing drinking water nanofiltration processes and the limited functionality of ultraviolet light alone, this invention proposes a coupled UV-nanofiltration water purification system. This system couples a UV emitter to the drinking water nanofiltration system, effectively preventing biological contamination of the nanofiltration membranes. Furthermore, the UV emitter is incorporated into the photocatalytic cell to enhance catalytic oxidation, providing a highly efficient and reliable method for treating brine, achieving near-zero discharge of nanofiltration brine.

[0007] The present invention proposes an ultraviolet-nanofiltration coupled water purification system, which specifically includes a pretreatment unit, a doser, an ultraviolet-nanofiltration coupling device, a sedimentation removal system, a roll-type nanofiltration membrane device and a pollutant treatment system. The pretreatment unit and the doser are connected. After pretreatment and one-time dosing, the raw water is filtered and sent to the ultraviolet-nanofiltration coupling device; the ultraviolet-nanofiltration coupling device includes a plurality of membrane elements and an ultraviolet emission device. The membrane elements are arranged inside the ultraviolet-nanofiltration coupling device. The raw water is separated into drinking water and concentrated water by nanofiltration of the plurality of membrane elements. The ultraviolet emission device emits ultraviolet rays to disinfect the membrane elements; the ultraviolet-nanofiltration coupling device, the sedimentation removal system, the roll-type nanofiltration membrane device and the pollutant treatment system are connected in sequence. The concentrated water generated by the ultraviolet-nanofiltration coupling device is filtered after removing sediments by the sedimentation removal system for secondary concentration and separation; the concentrated water separated for the second time enters the pollutant treatment system to remove pollutants.

[0008] Furthermore, the precipitation removal system includes a cathode area and a flat ceramic membrane pool of an ion exchange membrane electrolysis device, and the ultraviolet-nanofiltration coupling device, the cathode area, the flat ceramic membrane pool and the rolled nanofiltration membrane device are connected in sequence.

[0009] Furthermore, the pollutant treatment system includes a second dosing device, a photocatalytic reduction tank, an anode area of ​​an ion exchange membrane electrolysis device and a photocatalytic oxidation tank, and the rolled nanofiltration membrane device, the second dosing device, the photocatalytic reduction tank, the anode area and the photocatalytic oxidation tank are connected in sequence.

[0010] Furthermore, the pollutant treatment system also includes a nanofiltration concentrated water recovery device, and the photocatalytic oxidation tank is connected to the nanofiltration concentrated water recovery device.

[0011] Furthermore, a safety filter is provided between the doser and the UV-nanofiltration coupling device; a safety filter is provided between the precipitation removal system and the rolled nanofiltration membrane device; and a safety filter is provided between the photocatalytic oxidation tank and the nanofiltration concentrated water recovery device.

[0012] Furthermore, the doser 1 and the doser 2 are provided with static mixers.

[0013] Furthermore, both the photocatalytic reduction tank and the photocatalytic oxidation tank are provided with a second ultraviolet emission device and a stirring device.

[0014] Furthermore, the ultraviolet-nanofiltration coupling device includes a container, a plurality of membrane elements are arranged inside the container, and the membrane elements are ceramic cross-flow membrane elements; the ultraviolet emitting device includes an emitting device body and a plurality of optical fibers, and the optical fibers are arranged in the flow channel of the ceramic cross-flow membrane element; the two ends of the plurality of optical fibers are gathered into an optical fiber bundle, and the optical fiber bundle is connected to the emitting device body.

[0015] Furthermore, both ends of the container are tapered tubes, the upper end is provided with a raw water inlet, the middle is provided with a drinking water outlet, and the lower end is provided with a concentrated water outlet.

[0016] Furthermore, the ultraviolet-nanofiltration coupling device includes a container, a plurality of membrane elements are arranged inside the container, and the membrane elements are flat ceramic membrane elements; the ultraviolet emitting device includes a plurality of ultraviolet lamps, and the ultraviolet lamps are arranged between the flat ceramic membrane elements; the two ends of the container are conical tubes, both ends are provided with drinking water outlets, and the middle is provided with a raw water inlet and a concentrated water outlet.

[0017] The beneficial effects of the UV-nanofiltration coupled water purification system described in the present invention are:

[0018] (1) The UV-nanofiltration coupled water purification system described in the present invention overcomes the problem of biological contamination of nanofiltration membranes in existing drinking water nanofiltration processes. By providing a UV emission device in the nanofiltration device, ultraviolet light is used to directly disinfect the nanofiltration membrane, inhibiting the growth of microorganisms on the nanofiltration membrane, thereby increasing the life of the nanofiltration membrane and ensuring the safety of the produced water quality.

[0019] (2) The UV-nanofiltration coupled water purification system described in the present invention overcomes the problem of single function of ultraviolet light when used alone. It degrades organic matter in the concentrate before the membrane by irradiating the nanofiltration membrane with ultraviolet light, reduces organic pollution on the membrane surface, and improves membrane flux. By arranging ultraviolet emission devices in the photocatalytic reduction tank and the photocatalytic oxidation tank, new pollutants such as PFAS and antibiotics contained in the concentrated water are degraded under the action of ultraviolet light and chemicals. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0021] In the attached figure:

[0022] Figure 1 This is a process flow chart of a specific embodiment 1 of a UV-nanofiltration coupled water purification system according to the present invention;

[0023] Figure 2 This is a schematic diagram of the internal structure of the ultraviolet-nanofiltration coupling device in the first embodiment of the ultraviolet-nanofiltration coupled water purification system described in the present invention;

[0024] Figure 3 Schematic diagram of the structure of the ultraviolet-nanofiltration coupling device in the first embodiment of the ultraviolet-nanofiltration coupled water purification system according to the present invention;

[0025] Figure 4 This is a process flow chart of a second specific embodiment of a UV-nanofiltration coupled water purification system according to the present invention;

[0026] Figure 5 This is a schematic diagram of the internal structure of the ultraviolet-nanofiltration coupling device in the second specific embodiment of the ultraviolet-nanofiltration coupled water purification system described in the present invention;

[0027] Figure 6 This is a schematic structural diagram of the ultraviolet-nanofiltration coupling device in the second specific embodiment of the ultraviolet-nanofiltration coupled water purification system described in the present invention;

[0028] Figure 7 This is a schematic diagram of the arrangement structure of the flat ceramic membrane elements inside the UV-nanofiltration coupling device in the second specific embodiment of the UV-nanofiltration coupled water purification system described in the present invention;

[0029] Among them: 1-pretreatment unit, 2-dosing device 1, 3-security filter 1, 4-UV-nanofiltration coupling device, 5-emitter body, 6-ion exchange membrane electrolysis cathode area, 7-flat ceramic membrane pool, 8-security filter 2, 9-rolled nanofiltration membrane device, 10-dosing device 2, 11-photocatalytic reduction pool, 12-ion exchange membrane electrolysis anode area, 13-photocatalytic oxidation pool, 14-security filter 3, 15-nanofiltration concentrated water recovery device, 16-container, 17-mounting plate 1, 18-ceramic cross-flow membrane element, 19-optical fiber bundle, 20-optical fiber, 21-raw water inlet, 22-drinking water outlet, 23-concentrated water outlet, 24-flat ceramic membrane element, 25-UV lamp, 26-airtight joint, 27-coupler, 28-mounting plate 2, 29-power supply. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0033] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] Specific implementation method 1: See Figure 1-Figure 3The present embodiment is described in detail. The UV-nanofiltration coupled water purification system described in the present embodiment specifically includes a pretreatment unit 1, a doser 2, a UV-nanofiltration coupling device 4, a sedimentation removal system, a roll nanofiltration membrane device 9 and a pollutant treatment system. The pretreatment unit 1 is connected to the doser 2, and the raw water is pretreated in the pretreatment unit 1 to ensure that the natural organic matter content of the influent is less than 2 mg TOC / L, the turbidity is less than 1 NTU, and the SDI is less than 5. The pretreatment is one or more of pre-oxidation, coagulation, precipitation, adsorption, sand filtration, and a combination of these, and chlorine is added. Disinfectant is added to maintain the residual chlorine at a concentration of 0.5-1.0 mg / L for 20-30 minutes; the raw water that has completed pretreatment flows into the doser-2, and sodium metabisulfite solution is added through the doser-2 to inhibit microbial activity and dechlorinate; a security filter-3 is provided between the doser-2 and the UV-nanofiltration coupling device 4, and the raw water enters the security filter-3 to remove particulate impurities in the water, protect downstream equipment, and ensure that the nanofiltration membrane is not scratched by large particles of suspended matter; the filtered raw water flows into the UV-nanofiltration coupling device 4.

[0035] like Figure 2 As shown, the UV-nanofiltration coupling device 4 includes a container 16, a plurality of membrane elements and an UV emitting device 1, the two ends of the container 16 are tapered tubes, the upper end is provided with a raw water inlet 21, the middle is provided with a drinking water outlet 22, and the lower end is provided with a concentrated water outlet 23; two mounting plates 17 are provided inside the container 16, and a plurality of through holes are provided on the mounting plate 17; a plurality of membrane elements are evenly arranged between the two mounting plates 17, and the membrane element is a ceramic cross-flow membrane element 18, which is cylindrical as a whole, and is provided with a plurality of axial flow channels inside, and the cross section presents a honeycomb coal-like structure; the two ends of the ceramic cross-flow membrane element 18 are aligned and connected with the through holes on the mounting plate 17, and a sealing ring is provided at the connection, and the raw water flows into the flow channel in the ceramic cross-flow membrane element 18 through the through holes on the mounting plate 17; The external emitting device 1 includes an emitting device body 5 and several optical fibers 20. The optical fibers 20 are arranged in the flow channel of the ceramic cross-flow membrane element 18; the two ends of the several optical fibers 20 are gathered into an optical fiber bundle 19 under the action of the coupler 27. The optical fiber bundle 19 is sent to the outside of the container 16 and connected to the emitting device body 5 under the protection of the optical fiber protection tube. The ultraviolet rays emitted by the emitting device body 5 are transmitted through the optical fiber 20 and evenly distributed in the flow channel of the ceramic cross-flow membrane element 18, ensuring that the ultraviolet rays can effectively cover the water flowing through the membrane element to achieve the sterilization function and ensure the normal operation of the nanofiltration membrane. The sodium metabisulfite remaining in the water flow is catalytically oxidized by ultraviolet rays, and the function of advanced oxidation degradation of organic matter is achieved at the same time; an airtight joint 26 is provided in the optical fiber protection tube to prevent the raw water and drinking water separated by nanofiltration from flowing out of the optical fiber protection tube.

[0036] The raw water is separated into drinking water and concentrated water by nanofiltration through several ceramic cross-flow membrane elements 18. The drinking water flows out from the drinking water outlet 22, and the concentrated water flows out from the concentrated water outlet 23. The ultraviolet-nanofiltration coupling device 4, the sedimentation removal system, the rolled nanofiltration membrane device 9 and the pollutant treatment system are connected in sequence. The concentrated water produced by the ultraviolet-nanofiltration coupling device 4 is filtered after the sediment is removed by the sedimentation removal system and then passed into the rolled nanofiltration membrane device 9 for secondary concentration and separation. The concentrated water separated for the second time enters the pollutant treatment system to remove pollutants, and the drinking water separated for the second time is merged with the drinking water separated by the ultraviolet-nanofiltration coupling device 4.

[0037] The precipitation removal system includes the cathode area of ​​the ion exchange membrane electrolysis device and the flat ceramic membrane pool 7, and the ultraviolet-nanofiltration coupling device 4, the cathode area, the flat ceramic membrane pool 7 and the rolled nanofiltration membrane device 9 are connected in sequence; the concentrated water separated by the ultraviolet-nanofiltration coupling device 4 contains a large amount of calcium ions, magnesium ions and bicarbonate ions, and the concentrated water flows into the cathode area 6 of the ion exchange membrane electrolysis device, and the pH is adjusted to alkaline in the cathode area 6 of the ion exchange membrane electrolysis device, which will produce a large amount of inorganic precipitation, and then flows into the flat ceramic membrane pool 7 to remove the precipitation; a security filter 28 is provided between the flat ceramic membrane pool 7 and the rolled nanofiltration membrane device 9, and the large suspended particles in the concentrated water are removed by the security filter 28 to prevent the particulate impurities from affecting the water production performance of the subsequent rolled nanofiltration membrane; the concentrated water that has completed the precipitation filtration enters the rolled nanofiltration membrane device 9 for secondary nanofiltration separation.

[0038] The pollutant treatment system includes a dosing device 10, a photocatalytic reduction tank 11, an anode area of ​​an ion exchange membrane electrolysis device, and a photocatalytic oxidation tank 13. The rolled nanofiltration membrane device 9, the dosing device 10, the photocatalytic reduction tank 11, the anode area, and the photocatalytic oxidation tank 13 are connected in sequence. The concentrated water produced by the secondary nanofiltration separation is added with sodium bisulfite by the dosing device 10 and then enters the photocatalytic reduction tank 11, so that an oxygen-free environment can be spontaneously formed in the tank. There is no need to remove the dissolved oxygen in the concentrated water, and some new pollutants represented by PFAS are removed through the advanced reduction process. The effluent of the photocatalytic reduction tank 11 enters the anode area 12 of the ion exchange membrane electrolysis, and after adjusting the pH to acidic, it enters the photocatalytic oxidation tank 13. The photocatalytic oxidation tank 13 is provided with a stirring device to make the dissolved oxygen concentration higher than 1 mg / L, and some new pollutants represented by antibiotics are removed through the advanced oxidation process.

[0039] The photocatalytic reduction pool 11 and the photocatalytic oxidation pool 13 are both provided with a second ultraviolet emitting device and a stirring device. The second ultraviolet emitting device provides ultraviolet light to the photocatalytic reduction pool 11. The hydrated electrons generated by the ultraviolet-sulfite system formed have strong reducing properties. The fluorine atoms have a high electronegativity and are more prone to being attacked by electrons, thereby destroying the CF bonds in the PFAS and achieving degradation of the CC bonds. This greatly reduces the accumulation of fluorinated intermediates and achieves efficient defluorination and degradation of PFAS. The second ultraviolet emitting device provides ultraviolet light to the photocatalytic oxidation pool 13. The ultraviolet-bisulfite system formed will produce sulfate radicals and hydroxyl radicals under acidic and oxygen conditions. Sulfate radicals and hydroxyl radicals have high oxidation potentials and can oxidize and remove difficult-to-degrade organic matter such as antibiotics, decomposing them into small molecules.

[0040] The pollutant treatment system also includes a nanofiltration concentrated water recovery device 15, which is connected to the photocatalytic oxidation tank 13; a safety filter 3 14 is provided between the photocatalytic oxidation tank 13 and the nanofiltration concentrated water recovery device 15 to filter suspended particles in the effluent of the photocatalytic oxidation tank 13; after the photocatalytic reaction, the concentrated water contains a large amount of sulfate ions; the nanofiltration membrane in the nanofiltration concentrated water recovery device 15 has a small pore size and is negatively charged, and the sulfate retention rate can reach more than 95%; the sulfate ions are recovered and extracted through ion exchange resin technology to achieve resource utilization.

[0041] The doser 1 2 and the doser 2 10 are provided with a static mixer so that the added medicine can be fully mixed with the water.

[0042] The UV-nanofiltration coupled water purification system described in this embodiment is described by taking the purification of surface raw water as an example. The surface raw water is of Class III water quality. The specific treatment steps are as follows:

[0043] (1) First step of drug addition

[0044] Surface water typically contains 0.5 ppm of residual chlorine after passing through pretreatment unit 1. Filtered sodium metabisulfite solution is added to doser 2 for dechlorination. The concentration of the sodium metabisulfite solution is 1.5 ppm. The dosing point is located before safety filter 3 and is equipped with a static mixer to ensure thorough mixing with the treated water.

[0045] (2) UV-nanofiltration coupling device 4 treatment

[0046] The ceramic cross-flow membrane element 18 of the UV-nanofiltration coupling device 4 is a BA type ceramic element with a membrane area of ​​0.16m 2 The recovery rate of the device is 90%, and an external ultraviolet emission device with a wavelength of 254nm is connected.

[0047] (3) Concentrated water pretreatment unit

[0048] The concentrated water produced by the UV-nanofiltration coupling device 4 has a pH of 8.1, and contains 266 mg / L of calcium ions, 72 mg / L of magnesium ions, 695 mg / L of bicarbonate ions, 134 mg / L of chloride ions, 320 mg / L of sulfate ions, and 3 mg / L of dissolved oxygen.

[0049] After the concentrated water passes through the ion exchange membrane electrolysis cathode area 6 and the pH is adjusted to 10, calcium carbonate precipitation, magnesium carbonate precipitation and magnesium hydroxide precipitation will be produced. The subsequent flat ceramic membrane pool 7 is responsible for removing these precipitations.

[0050] The second safety filter 8 removes large suspended solids in the concentrated water, and the effluent satisfies SDI≤5 without causing damage to the rolled nanofiltration membrane device 9.

[0051] The rolled nanofiltration membrane device 9 further concentrates the concentrated water, and the produced drinking water is combined with the drinking water produced by the ultraviolet-nanofiltration coupling device 4 for use.

[0052] (4) Second step of drug addition

[0053] The doser 2 10 is responsible for adding sodium bisulfite. Sodium bisulfite with a concentration of 1mM is added to the concentrated water to serve as a reactant for the photocatalytic reaction.

[0054] (5) Photocatalytic treatment of concentrated water

[0055] A second UV emitter with a wavelength of 185 nm is placed at the center of photocatalytic reduction tank 11, along with a stirring device to ensure uniform UV exposure to the concentrated water. The UV-sulfite system in photocatalytic reduction tank 11 spontaneously consumes dissolved oxygen, creating an anaerobic environment. This allows for a reduction reaction and degrades new pollutants such as PFAS. The final photodecomposition products of a portion of the added bisulfite are sulfate and dithionate ions.

[0056] The effluent from the photocatalytic reduction tank 11 enters the ion exchange membrane electrolysis anode zone 12, where it is adjusted to a pH between 4 and 6 before flowing into the photocatalytic oxidation tank. A 254nm UV emitter is placed in the center of the oxidation tank, along with a stirring device. Air is introduced, and dissolved oxygen is injected into the concentrated water. This generates sulfate radicals in the UV-bisulfite system, triggering an oxidation reaction that degrades new pollutants such as antibiotics.

[0057] (6) Nanofiltration concentrated water recovery device 15

[0058] The photocatalytic pool contains more sulfate ions, and the nanofiltration membrane has a good interception capacity for divalent ions. After the concentrated water flows through the nanofiltration concentrated water recovery device 15, concentrated water containing more sulfate ions can be obtained. +Type and D301-SC OH resin, the resin will be respectively + With SO4 2- An exchange reaction occurs to obtain a resin containing sodium sulfate. Finally, the ion exchange resin is eluted to obtain sodium sulfate.

[0059] Specific implementation method 2: See Figure 4-Figure 7 The present embodiment is described in detail. The UV-nanofiltration coupling device 4 of the UV-nanofiltration coupled water purification system described in this embodiment includes a container 16 having two tapered tubes at both ends, each provided with a drinking water outlet 22, and a raw water inlet 21 and a concentrated water outlet 23 in the middle. Two mounting plates 28 are disposed within the container 16, with a plurality of membrane elements 24 spaced equidistantly between the two mounting plates 28. The membrane elements are flat ceramic membrane elements 24 having a rectangular cross-section and an internal rectangular flow channel. A UV emitting device 1 includes a plurality of UV lamps 25, with multiple UV lamps 25 disposed in the gaps between each flat ceramic membrane element 24. The UV lamps 25 are connected to a power source 29 via wires. The UV lamps 25 radiate UV light toward the surface of the flat ceramic membrane elements 24, sterilizing the surface of the flat ceramic membrane elements 24 and ensuring the normal operation of the nanofiltration membrane. The residual sodium metabisulfite in the water flow is catalytically oxidized by the UV light, thereby achieving the advanced oxidation degradation of organic matter. The other components and connection relationships of this embodiment are the same as those of the first embodiment.

[0060] The UV-nanofiltration coupled water purification system described in this embodiment is described by taking the purification of underground raw water as an example. The underground raw water is of Class II water quality. The specific treatment steps are as follows:

[0061] (1) First step of drug addition

[0062] After pretreatment, groundwater typically contains 0.5 ppm of residual chlorine. Filtered sodium metabisulfite solution is added to Doser-2 for dechlorination. Because the groundwater's dissolved oxygen content is low, sodium metabisulfite consumption is minimal, allowing the dosing concentration to be reduced to 1.0 ppm. The dosing point is located before Safety Filter-3 and is equipped with a static mixer to ensure thorough mixing with the treated water.

[0063] (2) UV-nanofiltration coupling device 4 treatment

[0064] The UV-nanofiltration coupling device 4 is in the form of coupling a flat ceramic membrane element 24 with an UV lamp 25, such as Figure 4 The device contains multiple vertically evenly arranged flat ceramic membrane elements 24, with the gaps between the flat ceramic membrane elements 24 filled with horizontally arranged ultraviolet lamps 25. The device has a recovery rate of 90%, and the ultraviolet lamps 25 emit ultraviolet light with a wavelength of 254nm.

[0065] (3) Concentrated water pretreatment unit

[0066] The concentrated water produced by the UV-nanofiltration coupling device 4 has a pH of 8.1, and contains 266 mg / L of calcium ions, 72 mg / L of magnesium ions, 695 mg / L of bicarbonate ions, 134 mg / L of chloride ions, 320 mg / L of sulfate ions, and 2 mg / L of dissolved oxygen.

[0067] The concentrated water passes through the ion exchange membrane electrolysis cathode zone 6 and adjusts the pH to 10, which will produce calcium carbonate precipitates, magnesium carbonate precipitates, and magnesium hydroxide precipitates. The subsequent flat ceramic membrane tank 7 is responsible for removing these precipitates.

[0068] The second safety filter 8 removes large suspended solids in the concentrated water, and the effluent satisfies SDI≤5 without causing damage to the rolled nanofiltration membrane device 9.

[0069] The rolled nanofiltration membrane device 9 further concentrates the concentrated water, and the produced drinking water is combined with the drinking water produced by the ultraviolet-nanofiltration coupling device 4 for use.

[0070] (4) Second step of drug addition

[0071] The doser 2 10 is responsible for adding sodium bisulfite. Sodium bisulfite with a concentration of 1mM is added to the concentrated water to serve as a reactant for the photocatalytic reaction.

[0072] (5) Photocatalytic treatment of concentrated water

[0073] A second UV emitter with a wavelength of 185 nm is placed in the center of photocatalytic reduction tank 11, along with a stirring device to ensure uniform UV exposure to the concentrated water. The UV-sulfite system in photocatalytic reduction tank 11 spontaneously consumes dissolved oxygen, creating an anaerobic environment. This allows for a reduction reaction and degrades new pollutants such as PFAS. The final photodecomposition products of a portion of the added bisulfite are sulfate and dithionate ions.

[0074] The effluent from photocatalytic reduction tank 11 enters ion exchange membrane electrolysis anode zone 12, where it is adjusted to a pH between 4 and 6 before flowing into photocatalytic oxidation tank 13. A second ultraviolet (UV) emitter with a wavelength of 254 nm is placed in the center of photocatalytic oxidation tank 13. A stirring device is also installed, allowing air to flow in and dissolved oxygen to be injected into the concentrated water. This allows the UV-bisulfite system to generate sulfate radicals, which then undergoes an oxidation reaction, degrading new pollutants such as antibiotics.

[0075] (6) Nanofiltration concentrated water recovery device 15

[0076] The photocatalytic pool contains more sulfate ions, and the nanofiltration membrane has a good interception capacity for divalent ions. After the concentrated water flows through the nanofiltration concentrated water recovery device 15, concentrated water containing more sulfate ions can be obtained. +Type and D301-SC OH resin, the resin will be respectively + With SO4 2- An exchange reaction occurs to obtain a resin containing sodium sulfate. Finally, the ion exchange resin is eluted to obtain sodium sulfate.

[0077] To summarize the above implementation cases, the UV-nanofiltration coupled water purification system described in the present invention overcomes the problem of biological contamination of nanofiltration membranes in existing drinking water nanofiltration processes. By arranging a UV emission device in the nanofiltration device, ultraviolet rays can directly disinfect the nanofiltration membrane, inhibit the reproduction of microorganisms on the nanofiltration membrane, improve the service life of the nanofiltration membrane, and ensure the safety of the water quality of the produced water. The UV-nanofiltration coupled water purification system described in the present invention overcomes the problem of the single function of ultraviolet rays when used alone. Ultraviolet rays are irradiated in front of the nanofiltration membrane to degrade organic matter in the concentrate in front of the membrane, reduce organic contamination on the membrane surface, and improve membrane flux. By arranging UV emission devices in the photocatalytic reduction tank 11 and the photocatalytic oxidation tank 13, new pollutants such as PFAS and antibiotics contained in the concentrated water are degraded under the action of ultraviolet rays and chemicals.

[0078] The specific embodiments described above further illustrate the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is merely a specific embodiment of the present invention and is not intended to limit the invention. Reasonable combinations of the features described in the above embodiments are also possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A UV-nanofiltration coupled water purification system, characterized by: The invention comprises a pretreatment unit (1), a doser (2), an ultraviolet-nanofiltration coupling device (4), a sedimentation removal system, a roll-type nanofiltration membrane device (9) and a pollutant treatment system. The pretreatment unit (1) and the doser (2) are connected. After the raw water is pretreated and once dosed, it is filtered and sent to the ultraviolet-nanofiltration coupling device (4). The ultraviolet-nanofiltration coupling device (4) comprises a plurality of membrane elements and an ultraviolet emission device (1). The membrane elements are arranged inside the ultraviolet-nanofiltration coupling device (4). The raw water is separated into drinking water and concentrated water by nanofiltration of the plurality of membrane elements. The ultraviolet emission device (1) emits ultraviolet rays to disinfect the membrane elements. The ultraviolet-nanofiltration coupling device (4), the sedimentation removal system, the roll-type nanofiltration membrane device (9) and the pollutant treatment system are connected in sequence. The concentrated water generated by the ultraviolet-nanofiltration coupling device (4) is filtered after the sediment is removed by the sedimentation removal system and is then passed into the roll-type nanofiltration membrane device (9) for secondary concentration and separation. The concentrated water separated from the secondary concentration enters the pollutant treatment system to remove pollutants. The precipitation removal system comprises a cathode region and a flat ceramic membrane pool (7) of an ion exchange membrane electrolysis device, a UV-nanofiltration coupling device (4), a cathode region, a flat ceramic membrane pool (7) and a rolled nanofiltration membrane device (9) which are sequentially connected; The pollutant treatment system comprises a second dosing device (10), a photocatalytic reduction tank (11), an anode region of an ion exchange membrane electrolysis device and a photocatalytic oxidation tank (13), and the rolled nanofiltration membrane device (9), the second dosing device (10), the photocatalytic reduction tank (11), the anode region and the photocatalytic oxidation tank (13) are connected in sequence; The pollutant treatment system further comprises a nanofiltration concentrated water recovery device (15), and the photocatalytic oxidation tank (13) is connected to the nanofiltration concentrated water recovery device (15); The ultraviolet-nanofiltration coupling device (4) comprises a container (16), wherein a plurality of membrane elements are arranged inside the container (16), and the membrane elements are ceramic cross-flow membrane elements (18) or flat ceramic membrane elements (24); When the membrane element is a ceramic cross-flow membrane element (18), the ultraviolet emitting device comprises an emitting device body (5) and a plurality of optical fibers (20), wherein the optical fibers (20) are arranged in the flow channel of the ceramic cross-flow membrane element (18); the ends of the plurality of optical fibers (20) are gathered into an optical fiber bundle (19), and the optical fiber bundle (19) is connected to the emitting device body (5); the two ends of the container (16) are tapered tubes, the upper end is provided with a raw water inlet (21), the middle part is provided with a drinking water outlet (22), and the lower end is provided with a concentrated water outlet (23); When the membrane element is a flat ceramic membrane element (24), the ultraviolet emitting device includes a plurality of ultraviolet lamp tubes (25), and the ultraviolet lamp tubes (25) are arranged between the flat ceramic membrane elements (24); both ends of the container (16) are tapered tubes, both ends are provided with drinking water outlets (22), and the middle part is provided with a raw water inlet (21) and a concentrated water outlet (23).

2. The UV-nanofiltration coupled water purification system according to claim 1, characterized in that: A safety filter is provided between the doser (2) and the ultraviolet-nanofiltration coupling device (4); a safety filter is provided between the sedimentation removal system and the roll-type nanofiltration membrane device (9); and a safety filter is provided between the photocatalytic oxidation tank (13) and the nanofiltration concentrated water recovery device (15).

3. The UV-nanofiltration coupled water purification system according to claim 2, characterized in that: The doser 1 (2) and the doser 2 (10) are provided with static mixers.

4. The UV-nanofiltration coupled water purification system according to claim 1 or 2, characterized in that: The photocatalytic reduction pool (11) and the photocatalytic oxidation pool (13) are both provided with a second ultraviolet emitting device and a stirring device.

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