Ultraviolet-nanofiltration coupled water purification system

Abstract

The invention discloses an ultraviolet-nanofiltration coupled water purification system, relates to the technical field of water treatment, and solves the problems of biological pollution of a nanofiltration membrane in a drinking water nanofiltration process and single function due to independent use of ultraviolet rays. Raw water is subjected to pretreatment and primary dosing filtration and then is fed into an ultraviolet-nanofiltration coupling device; a first ultraviolet emitting device arranged in the ultraviolet-nanofiltration coupling device emits ultraviolet rays to disinfect the membrane element; the concentrated water generated by the ultraviolet-nanofiltration coupling device is subjected to precipitate removal and filtration, and then is introduced into the roll-type nanofiltration membrane device for secondary concentration and separation; the separated concentrated water enters a photocatalysis pool of the pollutant treatment system to remove pollutants under the combined action of a medicament and ultraviolet rays. The ultraviolet emission device is coupled into the drinking water nanofiltration device, biological pollution of a nanofiltration membrane is avoided, the catalytic oxidation reduction effect is enhanced, the ultraviolet emission device is arranged in the photocatalytic pool, the catalytic reduction effect and the catalytic oxidation effect are improved respectively, and the purpose of near-zero emission of nanofiltration concentrated water is achieved.

Description

Technical Field

[0001] The 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 has the characteristics of high separation effect and selective separation. It has been widely used in many fields such as drinking water purification, sewage reuse, and food processing. Especially in drinking water treatment, nanofiltration membrane can effectively remove large molecular organic matter and some inorganic ions in water, becoming 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 membrane. It is necessary to configure 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 the nanofiltration process, the pretreatment unit is generally disinfected with chlorine, which is used to inactivate microorganisms and prevent biological contamination. However, the presence of chlorine will cause oxidation damage to the nanofiltration membrane, so the effluent from the pretreatment unit must be dechlorinated before entering the membrane element. In the membrane element, due to the absence of bactericides such as residual chlorine, microbial contamination may occur on the surface of the nanofiltration membrane. This phenomenon will shorten the life of the nanofiltration membrane, affect the interception function of the membrane, and cannot ensure the drinking safety of the produced water. The control of biological contamination on the membrane surface has become one of the application bottlenecks of nanofiltration.

[0004] Through the membrane interception 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 perfluoroalkyl substances (PFAS), trace organic pollutants such as chloroform and its intermediates. The brine treatment faces problems such as complex water quality components and low biodegradability. At present, common brine treatment and disposal methods include entering the sewage treatment system, brine reinjection, ozone oxidation, and advanced oxidation processes combined with ozone. However, these methods still have many problems in practical applications, such as brine reinjection will increase the environmental burden, high oxidant dosage but poor effect, low water recovery rate and other limitations. The process concept mostly adopts a superposition method, with 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 the agent.

[0005] As a physical disinfection method, ultraviolet disinfection 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 water quality fluctuations. 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 lamps with a diameter of centimeters, and mainly focuses on the disinfection function, making it difficult to achieve the coupling application of multiple functions in one system. The existing technology still lacks a coupling process that can realize the coordinated application of disinfection, photocatalytic oxidation and photocatalytic reduction in one system. Summary of the invention

[0006] In order to solve the above-mentioned problems of biological contamination of nanofiltration membranes in existing drinking water nanofiltration processes and the single function of ultraviolet light alone, the present invention proposes a UV-nanofiltration coupled water purification system. The present invention couples the UV emission device to the drinking water nanofiltration device, effectively avoiding the situation of biological contamination of the nanofiltration membrane. At the same time, the UV emission device is arranged in the photocatalytic pool to improve the catalytic oxidation effect, providing an efficient and reliable concentrated water treatment method to achieve the goal of near-zero discharge of nanofiltration concentrated water.

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

[0008] Furthermore, the precipitation removal system includes a cathode region and a flat ceramic membrane pool of an ion exchange membrane electrolysis device, and the ultraviolet-nanofiltration coupling device, the cathode region, 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 arranged between the dosing device and the ultraviolet-nanofiltration coupling device; a safety filter is arranged between the precipitation removal system and the rolled nanofiltration membrane device; and a safety filter is arranged 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, the photocatalytic reduction pool and the photocatalytic oxidation pool are both provided with a second ultraviolet emitting device and a stirring device.

[0014] Furthermore, the UV-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 UV 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 conical 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 lamp tubes, and the ultraviolet lamp tubes 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 arranging a UV emission device in the nanofiltration device, ultraviolet rays are used to directly disinfect the nanofiltration membrane, inhibiting the reproduction of microorganisms on the nanofiltration membrane, thereby increasing the life of the nanofiltration membrane and ensuring the safety of the water quality of the produced water.

[0019] (2) The UV-nanofiltration coupled water purification system described in the present invention overcomes the problem of the single function of ultraviolet light when used alone. It degrades organic matter in the concentrate before the membrane by irradiating ultraviolet light in front of the nanofiltration membrane, 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 picture:

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

[0023] Figure 2 It is a schematic diagram of the internal structure of the ultraviolet-nanofiltration coupling device in the specific implementation mode 1 of the ultraviolet-nanofiltration coupling water purification system described in the present invention;

[0024] Figure 3 It is a structural schematic diagram of the ultraviolet-nanofiltration coupling device in the specific implementation mode 1 of the ultraviolet-nanofiltration coupling water purification system described in the present invention;

[0025] Figure 4 It is a process flow chart of a specific embodiment 2 of a UV-nanofiltration coupled water purification system according to the present invention;

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

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

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

[0029] Wherein: 1-pretreatment unit, 2-doser 1, 3-security filter 1, 4-ultraviolet-nanofiltration coupling device, 5-emitter body, 6-ion exchange membrane electrolysis cathode zone, 7-flat ceramic membrane pool, 8-security filter 2, 9-rolled nanofiltration membrane device, 10-doser 2, 11-photocatalytic reduction pool, 12-ion exchange membrane electrolysis anode zone, 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-ultraviolet lamp, 26-airtight joint, 27-coupler, 28-mounting plate 2, 29-power supply. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part 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 creative work are 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", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0032] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to 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 specifically described. 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 mgTOC / 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 used 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 the pretreatment flows into the doser-2, and sodium metabisulfite solution is added through the doser-2 to inhibit the activity of microorganisms and dechlorinate; a security filter-3 is arranged between the doser-2 and the ultraviolet-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 ultraviolet-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 conical tubes, a raw water inlet 21 is provided at the upper end, a drinking water outlet 22 is provided in the middle, and a concentrated water outlet 23 is provided at the lower end; two mounting plates 17 are provided inside the container 16, and a plurality of through holes are provided on the mounting plates 17; a plurality of membrane elements are evenly provided between the two mounting plates 17, and the membrane element is a ceramic cross-flow membrane element 18, which is columnar 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 transmitting device 1 includes a transmitting device body 5 and a plurality of 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 plurality of optical fibers 20 are gathered into an optical fiber bundle 19 under the action of a coupler 27. The optical fiber bundle 19 is sent to the outside of the container 16 and connected to the transmitting device body 5 under the protection of an optical fiber protection tube. The ultraviolet rays emitted by the transmitting device body 5 are transmitted through the optical fiber 20, and the ultraviolet rays are evenly distributed in the flow channel in 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 arranged in the optical fiber protection tube to prevent the raw water and the 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 a number of 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 combined with the drinking water separated by the ultraviolet-nanofiltration coupling device 4.

[0037] The precipitation removal system includes a cathode area and a flat ceramic membrane pool 7 of an ion exchange membrane electrolysis device, and an ultraviolet-nanofiltration coupling device 4, a cathode area, a flat ceramic membrane pool 7 and a 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 2 8 is arranged 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 2 8 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 doser 10, a photocatalytic reduction tank 11, an anode area of ​​an ion exchange membrane electrolysis device, and a photocatalytic oxidation tank 13. The roll nanofiltration membrane device 9, the doser 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 enters the photocatalytic reduction tank 11 after sodium bisulfite is added to the doser 10, so that an anaerobic environment can be spontaneously formed in the tank, and there is no need to remove the dissolved oxygen in the concentrated water. Some new pollutants represented by PFAS are removed through advanced reduction processes. 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. A stirring device is provided in the photocatalytic oxidation tank 13 to make the dissolved oxygen concentration higher than 1 mg / L, and some new pollutants represented by antibiotics are removed through advanced oxidation processes.

[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 electronegativity of fluorine atoms is very high and they are more likely to be attacked by electrons, thereby destroying the CF bond in PFAS and achieving degradation of the CC bond, which 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 antibiotics and other difficult-to-degrade organic matter, decomposing them into small molecules.

[0040] The pollutant treatment system also includes a nanofiltration concentrated water recovery device 15, and the photocatalytic oxidation tank 13 is connected to the nanofiltration concentrated water recovery device 15; a security filter 3 14 is arranged between the photocatalytic oxidation tank 13 and the nanofiltration concentrated water recovery device 15 to filter the suspended particles in the effluent of the photocatalytic oxidation tank 13; after the photocatalytic reaction, the concentrated water contains more 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 agent can be fully mixed with the water.

[0042] The ultraviolet-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 Class III water quality. The specific treatment steps are:

[0043] (1) First step: dosing treatment

[0044] The surface raw water generally contains 0.5ppm residual chlorine after the pretreatment unit 1. The filtered sodium pyrosulfite solution is added to the dosing device 2 for dechlorination treatment. The concentration of the sodium pyrosulfite solution is 1.5ppm. The dosing point is located before the security filter 3, and a static mixer is set to ensure that it is completely mixed with the water to be treated.

[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 ​​0.16 m 2 The recovery rate of the device is 90%, and an external ultraviolet emitting 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 security filter 2 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: dosing treatment

[0053] The doser 2 10 is responsible for adding sodium bisulfite. Sodium bisulfite with a concentration of 1 mM 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 ultraviolet emitting device with a wavelength of 185 nm is placed in the center of the photocatalytic reduction tank 11, and a stirring device is installed so that the concentrated water is evenly irradiated with ultraviolet light. The ultraviolet-sulfite system in the photocatalytic reduction tank 11 spontaneously consumes dissolved oxygen, forms an anaerobic environment, undergoes a reduction reaction, and degrades new pollutants such as PFAS. The final photodecomposition products of a portion of the added bisulfite are sulfate ions and dithionate ions.

[0056] The effluent from the photocatalytic reduction pool 11 enters the ion exchange membrane electrolysis anode area 12, and after adjusting the pH to 4-6, it flows into the photocatalytic oxidation pool. A UV emission device with a wavelength of 254nm is placed in the center of the oxidation pool, and a stirring device is installed to introduce air and inject dissolved oxygen into the concentrated water, so that the UV-bisulfite system produces sulfate free radicals, an oxidation reaction occurs, and new pollutants such as antibiotics are degraded.

[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 ultraviolet-nanofiltration coupling device 4 of the ultraviolet-nanofiltration coupling water purification system described in the present embodiment includes a container 16, the two ends of the container 16 are conical tubes, both ends are provided with drinking water outlets 22, and the middle is provided with a raw water inlet 21 and a concentrated water outlet 23; two mounting plates 28 are provided inside the container 16, and a plurality of membrane elements are equidistantly provided between the two mounting plates 28, and the membrane elements are flat ceramic membrane elements 24, and the flat ceramic membrane elements 24 have a rectangular cross section and are provided with rectangular flow channels inside; the ultraviolet emitting device 1 includes a plurality of ultraviolet lamp tubes 25, and a plurality of ultraviolet lamp tubes 25 are provided in the gaps between each flat ceramic membrane element 24, and the ultraviolet lamp tubes 25 are connected to a power supply 29 through a wire; the ultraviolet lamp tubes 25 radiate ultraviolet rays to the surface of the flat ceramic membrane element 24, realize the sterilization function of the surface of the flat ceramic membrane element 24, ensure the normal operation of the nanofiltration membrane, and the sodium pyrosulfite remaining in the water flow is catalytically oxidized by ultraviolet rays, and the function of advanced oxidation degradation of organic matter is realized at the same time. The other components and connection relationships of this embodiment are the same as those of the first embodiment.

[0060] The ultraviolet-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 Class II water quality. The specific treatment steps are:

[0061] (1) First step: dosing treatment

[0062] The underground raw water generally contains 0.5ppm residual chlorine after the pretreatment unit. The filtered sodium pyrosulfite solution is added to the dosing device 2 for dechlorination. Because the dissolved oxygen content of the underground raw water is low, the consumption of sodium pyrosulfite is small, and the dosing concentration can be reduced to 1.0ppm. The dosing point is located before the security filter 3, and a static mixer is set to ensure that it is completely mixed with the water to be treated.

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

[0064] The UV-nanofiltration coupling device 4 is in the form of a flat ceramic membrane element 24 coupled with an UV lamp 25, such as Figure 4 As shown, there are multiple vertically evenly arranged flat ceramic membrane elements 24 inside the device, and the gaps between the flat ceramic membrane elements 24 are filled with horizontally arranged ultraviolet lamps 25. The recovery rate of the device is 90%, and the ultraviolet lamps 25 emit ultraviolet rays 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 cathode area 6 of the ion exchange membrane electrolysis and adjusts the pH to 10, which will produce calcium carbonate precipitation, magnesium carbonate precipitation and magnesium hydroxide precipitation. The subsequent flat ceramic membrane pool 7 is responsible for removing these precipitations.

[0068] The security filter 2 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: dosing treatment

[0071] The doser 2 10 is responsible for adding sodium bisulfite. Sodium bisulfite with a concentration of 1 mM 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 ultraviolet emitting device with a wavelength of 185 nm is placed in the center of the photocatalytic reduction tank 11, and a stirring device is installed so that the concentrated water is evenly irradiated with ultraviolet rays. The ultraviolet-sulfite system in the photocatalytic reduction tank 11 spontaneously consumes dissolved oxygen, forms an anaerobic environment, undergoes a reduction reaction, and degrades new pollutants such as PFAS. The final photodecomposition products of a portion of the added bisulfite are sulfate ions and dithionate ions.

[0074] The effluent from the photocatalytic reduction pool 11 enters the ion exchange membrane electrolysis anode area 12, and after adjusting the pH to 4-6, flows into the photocatalytic oxidation pool 13. A second ultraviolet emission device with a wavelength of 254nm is placed in the center of the photocatalytic oxidation pool 13, and a stirring device is installed to introduce air and inject dissolved oxygen into the concentrated water, so that the ultraviolet-bisulfite system produces sulfate free radicals, an oxidation reaction occurs, and new pollutants such as antibiotics are degraded.

[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, increase the 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 alone. Organic matter in the concentrate before the membrane is degraded by ultraviolet rays irradiating in front of the nanofiltration membrane, organic contamination on the membrane surface is reduced, and membrane flux is increased. 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 purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the invention. It can also be a reasonable combination of the features recorded in the above implementation methods. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A UV-nanofiltration coupled water purification system, characterized in that: 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 pretreatment and a primary dosing, the raw water is filtered and then 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 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 roll-type nanofiltration membrane device (9) for secondary concentration and separation. The concentrated water separated by the secondary concentration enters the pollutant treatment system to remove pollutants.

2. The UV-nanofiltration coupled water purification system according to claim 1, characterized in that: The precipitation removal system comprises a cathode region and a flat ceramic membrane pool (7) of an ion exchange membrane electrolysis device, and an ultraviolet-nanofiltration coupling device (4), a cathode region, a flat ceramic membrane pool (7) and a rolled nanofiltration membrane device (9) are sequentially connected.

3. The UV-nanofiltration coupled water purification system according to claim 1, characterized in that: The pollutant treatment system comprises a second dosing device (10), a photocatalytic reduction pool (11), an anode region of an ion exchange membrane electrolysis device and a photocatalytic oxidation pool (13), and the rolled nanofiltration membrane device (9), the second dosing device (10), the photocatalytic reduction pool (11), the anode region and the photocatalytic oxidation pool (13) are connected in sequence.

4. The UV-nanofiltration coupled water purification system according to claim 3, characterized in that: 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).

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

6. The UV-nanofiltration coupled water purification system according to claim 5, characterized in that: The doser 1 (2) and the doser 2 (10) are provided with a static mixer.

7. The UV-nanofiltration coupled water purification system according to claim 3, 4 or 5, 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.

8. The UV-nanofiltration coupled water purification system according to claim 1, characterized in that: The ultraviolet-nanofiltration coupling device (4) comprises a container (16), wherein a plurality of membrane elements are arranged inside the container (16), wherein the membrane elements are ceramic cross-flow membrane elements (18); the first 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); and the two ends of the plurality of optical fibers (20) are gathered into an optical fiber bundle (19), wherein the optical fiber bundle (19) is connected to the emitting device body (5).

9. The UV-nanofiltration coupled water purification system according to claim 8, characterized in that: The two ends of the container (16) are conical 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).

10. The UV-nanofiltration coupled water purification system according to claim 1, characterized in that: 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 flat ceramic membrane elements (24); the ultraviolet emitting device comprises a plurality of ultraviolet lamp tubes (25), and the ultraviolet lamp tubes (25) are arranged between the flat ceramic membrane elements (24); the two ends of the container (16) are conical tubes, and 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).

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