A local enhanced electric field nanofiltration drinking water treatment device and method

Abstract

A local enhanced electric field nanofiltration drinking water treatment device and method thereof, relating to the technical field of drinking water treatment. The device solves the problems that the existing drinking water disinfectant has strong oxidation performance, the nanofiltration membrane has weak oxidation resistance, and the disinfection process and the nanofiltration process are difficult to be compatible. The drinking water treatment device includes a raw water tank, a LEEFT unit and a nanofiltration unit; the raw water tank is used to convey raw water to the LEEFT unit; the LEEFT unit is used to remove particulate matter and bacteria in the raw water, and convey the raw water after the particulate matter and bacteria are removed to the nanofiltration unit; the nanofiltration unit is used to deeply process the raw water into clear water and concentrated water, and is also used to repeatedly treat the concentrated water. The present invention is suitable for the treatment of drinking water.

Description

Technical Field

[0001] The invention relates to the technical field of drinking water treatment. Background Art

[0002] As a high-pressure driven membrane, nanofiltration can not only remove particulate matter in water, but also effectively intercept a variety of inorganic salts and small molecules in water. It has the advantages of efficient separation, stable water output, high integration and automated operation and maintenance. However, the problem of biological contamination of nanofiltration membranes limits its large-scale application.

[0003] In order to solve the problem of biological fouling of nanofiltration membranes, researchers usually couple the ultrafiltration process as a pretreatment to effectively alleviate the biological fouling of nanofiltration membranes. However, due to the secondary growth characteristics of microorganisms, the intermediate water tank between ultrafiltration and nanofiltration is prone to breed microorganisms during long-term use, leading to biological fouling of nanofiltration membranes. The use of chemical disinfectants such as sodium hypochlorite and chlorine dioxide will increase the residence time of water treatment, and the strong oxidizing effect of disinfectants can easily cause irreversible effects on membrane pores, shortening the service life of nanofiltration membranes. Although heating pasteurization, ultraviolet radiation or ionizing radiation, and plasma treatment are relatively effective in inactivating microorganisms, these methods are costly and difficult to apply continuously to drinking water treatment. Therefore, it is urgent to develop a simple and efficient physical disinfection method as a pretreatment for the nanofiltration process to ensure the long-term and stable operation of the nanofiltration process. Summary of the invention

[0004] The present invention provides a local enhanced electric field nanofiltration drinking water treatment device, which solves the problems that the existing drinking water disinfectant has strong oxidation performance, the nanofiltration membrane has weak oxidation resistance, and the disinfection process and the nanofiltration process are difficult to be compatible.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides a local enhanced electric field nanofiltration drinking water treatment device, the device comprising a raw water tank, a LEEFT unit and a nanofiltration unit;

[0007] The raw water tank is used to deliver raw water to the LEEFT unit;

[0008] The LEEFT unit is used to remove particles and bacteria from raw water, and to deliver the raw water after the particles and bacteria are removed to the nanofiltration unit;

[0009] The nanofiltration unit is used for deeply treating raw water to produce clean water and concentrated water, and is also used for repeatedly treating the concentrated water.

[0010] Further, in a preferred embodiment, the LEEFT unit comprises a DC power supply and a LEEFT reactor;

[0011] The LEEFT reactor comprises an anode, a flow guide net and a cathode;

[0012] The guide net is used to isolate the anode and the cathode;

[0013] The DC power supply is used to provide a DC voltage to the anode and the cathode;

[0014] The anode and cathode are used to remove particulate matter in raw water, and are also used to amplify the DC voltage to thousands of volts through the local enhanced electric field to remove bacteria in the raw water, and transport the raw water after the particulate matter and bacteria are removed to the nanofiltration unit.

[0015] Furthermore, in a preferred embodiment, the surface area of ​​the guide net is larger than the area of ​​the anode and the cathode;

[0016] The materials of the anode and cathode are copper phosphide nanowires Cu3PNWs.

[0017] Furthermore, in a preferred embodiment, the nanofiltration unit comprises a nanofiltration integrated device, a permeate outlet flow control valve, a concentrate outlet flow control valve, a concentrate tank and a production water tank;

[0018] The nanofiltration integrated equipment is used to deeply treat the raw water and deliver the treated clean water to the water production tank, and also to deliver the treated concentrated water to the concentrated water tank, and also to repeatedly treat the concentrated water;

[0019] The permeate outlet flow control valve is connected in series to the nanofiltration integrated device and the water production tank to control the outlet flow;

[0020] The concentrate outlet flow control valve is connected in series to the nanofiltration integrated device and the concentrate tank to control the outlet flow.

[0021] Furthermore, in a preferred embodiment, the device further comprises a water supply pump, a first pressure gauge and a water inlet flow control valve;

[0022] The water feed pump is used to deliver the raw water in the raw water tank to the LEEFT reactor;

[0023] The first pressure gauge is connected in series to the LEEFT reactor to detect and display raw water pressure data;

[0024] The water inlet flow control valve is connected in series to the water supply pump and the first pressure gauge to control the water outlet flow.

[0025] Furthermore, in a preferred embodiment, the device further comprises a water inlet flow control valve, a rotor flow meter, a second pressure gauge and a pressure pump;

[0026] The water inlet flow control valve is connected in series to the water outlet of the LEEFT reactor to control the water outlet flow;

[0027] The rotor flowmeter is connected in series to the water outlet of the water inlet flow control valve, and is used to detect and display the water flow;

[0028] The pressure pump is connected in series to the water outlet of the rotor flowmeter, and is used to transport raw water to the nanofiltration unit;

[0029] The second pressure gauge is connected in series to the rotor flowmeter and the pressure pump, and is used to detect and display the water pressure.

[0030] Furthermore, in a preferred embodiment, the device further comprises a PLC control cabinet;

[0031] The PLC control cabinet is used to control the drinking water treatment device to perform automated treatment.

[0032] The present invention also provides a method for treating drinking water with a local enhanced electric field nanofiltration, which is implemented based on a local enhanced electric field nanofiltration drinking water treatment device as described in any one of the above, and the method is:

[0033] S1. Use LEEFT unit to remove particles and bacteria from raw water;

[0034] S2. Use nanofiltration unit to deeply treat the raw water after removing particles and bacteria to obtain clean water.

[0035] Furthermore, in another preferred embodiment, the preparation method of the copper phosphide nanowires Cu3PNWs in the LEEFT unit in the above step S1 is:

[0036] S11, washing the copper foam with HCl to remove the oxide layer on the surface of the copper foam;

[0037] S12, washing the foamed copper with deionized water to remove the oxide layer, and then washing with anhydrous ethanol to remove organic matter on the surface of the copper oxide;

[0038] S13, using nitrogen to purge to remove organic copper oxide, and then placing it in sodium hydroxide solution, using chronopotentiometry to obtain Cu(OH)2NWs;

[0039] S14, using sodium phosphite to react with the Cu(OH)2NWs to obtain copper phosphide nanowires Cu3PNWs.

[0040] Furthermore, in a preferred embodiment, the nanofiltration unit in the above step S2 adopts a three-stage series operation mode, the concentrated water from the previous stage of nanofiltration is used as the influent water for the next stage, the three stages of produced water are merged, and the concentrated water is repeatedly treated.

[0041] The beneficial effects of the present invention are:

[0042] 1. The present invention provides a local enhanced electric field nanofiltration drinking water treatment device, which adopts a LEEFT unit to remove particulate matter and bacteria in raw water. The LEEFT unit, as an electrochemical disinfection method, can avoid damage to the nanofiltration membrane by traditional disinfectants; the Cu3PNWs in the LEEFT unit can remove suspended particulate matter through physical screening to alleviate membrane pollution; it has high disinfection efficiency, high water flux, and the hydraulic retention time can be controlled within 3 seconds; it also has the advantages of low energy consumption and applied voltage as low as 1.0 to 2.0 V, so that the local enhanced electric field nanofiltration drinking water treatment device described in this embodiment has the characteristics of easy operation, simple design, small footprint and stable operation.

[0043] 2. Existing chemical or physical methods are used to solve the problem of biological contamination caused by nanofiltration membranes removing particles and bacteria from water. However, chemical methods will have irreversible effects on the membrane structure due to their strong oxidizing effect, shortening the service life of the nanofiltration membrane; physical methods have the problems of inability to work continuously and high equipment costs. The present invention provides a local enhanced electric field nanofiltration drinking water treatment device, which uses LEEFT units and nanofiltration units to double-treat raw water, improves the quality of effluent water, solves the problem of biological contamination, and also avoids the problems of shortening the service life of the nanofiltration membrane, inability to work continuously, and high equipment costs caused by chemical methods and physical methods, respectively, because the LEEFT unit is a nanowire-driven electrochemical disinfection method.

[0044] The invention is suitable for treating drinking water. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a structural schematic diagram of a local enhanced electric field nanofiltration drinking water treatment device according to embodiments one to seven;

[0046] Figure 2 It is a process flow chart of a local enhanced electric field nanofiltration drinking water treatment method described in Implementation Mode 8;

[0047] Figure 3 The inactivation efficiency of microorganisms of a local enhanced electric field nanofiltration drinking water treatment device at different operating times as described in the eleventh embodiment;

[0048] Figure 4 This is a chart of the operating environment limits of the membrane elements in the nanofiltration unit described in the eleventh embodiment.

[0049] Among them, 1-raw water tank, 2-water feed pump, 3-water inlet flow control valve, 4-first pressure gauge, 5-DC power supply, 6-LEEFT reactor, 7-anode, 8-flow guide net, 9-cathode, 10-water inlet flow control valve, 11-rotor flowmeter, 12-second pressure gauge, 13-pressure pump, 14-nanofiltration integrated equipment, 15-permeate outlet flow control valve, 16-concentrate outlet flow control valve, 17-concentrate tank, 18-product water tank, 19-PLC control cabinet. DETAILED DESCRIPTION

[0050] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0051] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0052] It should also be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, the singular forms "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise.

[0053] The specific implementation mode of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

[0054] Implementation method 1. See Figure 1 This embodiment is described. This embodiment provides a local enhanced electric field nanofiltration drinking water treatment device, the drinking water treatment device includes a raw water tank 1, a LEEFT unit and a nanofiltration unit;

[0055] The raw water tank 1 is used to deliver raw water to the LEEFT unit;

[0056] The LEEFT unit is used to remove particles and bacteria from raw water, and to deliver the raw water after the particles and bacteria are removed to the nanofiltration unit;

[0057] The nanofiltration unit is used for deeply treating raw water to produce clean water and concentrated water, and is also used for repeatedly treating the concentrated water.

[0058] In practical application, if Figure 1 As shown, the raw water tank 1 is connected to the LEEFT unit through a water inlet pipeline, so that the raw water tank 1 is used to transport raw water to the LEEFT unit; the LEEFT unit is used to remove particulate matter and bacteria in the raw water, and transport the raw water after the particulate matter and bacteria are removed to the nanofiltration unit; the nanofiltration unit is used to deeply treat the raw water to produce clear water and concentrated water, and also adopts a three-stage series operation mode, the concentrated water of the previous stage of nanofiltration is used as the inlet water of the next stage, the three stages of produced water are merged, and the concentrated water is repeatedly treated, so that the nanofiltration operation recovery rate reaches 50%.

[0059] The present embodiment provides a locally enhanced electric field nanofiltration drinking water treatment device, which adopts a LEEFT unit to remove particulate matter and bacteria in raw water, wherein the LEEFT unit, as an electrochemical disinfection method, can avoid damage to the nanofiltration membrane by traditional disinfectants; the Cu3PNWs in the LEEFT unit can remove suspended particulate matter through physical screening and alleviate membrane pollution; it has high disinfection efficiency, high water flux, and the hydraulic retention time can be controlled within 3 seconds; it also has the advantages of low energy consumption and applied voltage as low as 1.0~2.0V, so that the locally enhanced electric field nanofiltration drinking water treatment device described in the present embodiment has the characteristics of easy operation, simple design, small footprint and stable operation.

[0060] Implementation method 2. See Figure 1 This embodiment is described as follows: This embodiment is an example of the LEEFT unit in the local enhanced electric field nanofiltration drinking water treatment device described in the first embodiment;

[0061] The LEEFT unit includes a DC power supply 5 and a LEEFT reactor 6;

[0062] The LEEFT reactor 6 comprises an anode 7, a flow guide net 8 and a cathode 9;

[0063] The guide net 8 is used to isolate the anode 7 and the cathode 9;

[0064] The DC power supply 5 is used to provide a DC voltage to the anode 7 and the cathode 9;

[0065] The anode 7 and cathode 9 are used to remove particulate matter in raw water, and are also used to amplify the DC voltage to thousands of volts through the local enhanced electric field to remove bacteria in the raw water, and transport the raw water after the particulate matter and bacteria are removed to the nanofiltration unit.

[0066] In practical application, if Figure 1 As shown, the LEEFT unit includes a DC power supply 5 and a LEEFT reactor 6; the interior of the LEEFT reactor 6 is composed of an anode 7, a guide net 8 and a cathode 9, wherein the anode 7 and the cathode 9 are foam copper, and the suspended particles in the raw water are removed under the pore screening effect of the foam copper; at the same time, the external constant voltage DC power supply 5 makes it possible for the anode 7 and the cathode 9 to be connected to the DC power supply. After the anode 7 and the cathode 9 are connected to the DC power supply, the anode 7 and the cathode 9 amplify the 1-2.0V voltage provided by the DC power supply to thousands of volts through the local enhanced electric field effect, which exceeds the breakdown threshold of the transmembrane potential of the microorganism, thereby inducing the electroporation effect, causing irreversible damage to the microorganisms and bacteria, and then leading to the death of the microorganisms and bacteria.

[0067] Implementation method 3. See Figure 1 This embodiment is described. This embodiment is an example of the surface area of ​​the guide net 8 and the materials of the anode 7 and the cathode 9 in the local enhanced electric field nanofiltration drinking water treatment device described in the second embodiment.

[0068] The surface area of ​​the guide net 8 is larger than the area of ​​the anode 7 and the cathode 9;

[0069] The material of the anode 7 and the cathode 9 is copper phosphide nanowires Cu3PNWs.

[0070] In practical application, if Figure 1 As shown, the surface area of ​​the guide mesh 8 is larger than the area of ​​the anode 7 and the cathode 9, so as to fully isolate the electrodes and prevent short circuit.

[0071] The material of the anode 7 and the cathode 9 is copper phosphide nanowires Cu3PNWs, wherein the copper phosphide nanowires Cu3PNWs are made from copper foam as raw material through electrochemical anodic oxidation combined with phosphating steps. The Cu3PNWs surface nanowires amplify the 1-2.0V voltage provided by the DC power supply to thousands of volts through the local enhanced electric field effect, exceeding the breakdown threshold of the transmembrane potential of the microorganism, thereby inducing the electroporation effect, causing irreversible damage to the microorganisms and bacteria, and then leading to the death of the microorganisms and bacteria.

[0072] Implementation method 4. See Figure 1 This embodiment is described. This embodiment is an example of a nanofiltration unit in a local enhanced electric field nanofiltration drinking water treatment device described in Embodiment 3.

[0073] The nanofiltration unit includes a nanofiltration integrated device 14, a permeate outlet flow control valve 15, a concentrate outlet flow control valve 16, a concentrate water tank 17 and a production water tank 18;

[0074] The nanofiltration integrated device 14 is used to perform deep treatment on raw water and deliver the treated clean water to the water production tank 18, and also to deliver the treated concentrated water to the concentrated water tank 17, and also to repeatedly treat the concentrated water;

[0075] The permeate outlet flow control valve 15 is connected in series to the nanofiltration integrated device 14 and the water production tank 18 to control the outlet flow;

[0076] The concentrate outlet flow control valve 16 is connected in series to the nanofiltration integrated device 14 and the concentrate tank 17 to control the outlet flow.

[0077] In practical application, if Figure 1 As shown, the nanofiltration unit includes a nanofiltration integrated device 14, a permeate outlet flow control valve 15, a concentrate outlet flow control valve 16, a concentrate water tank 17 and a production water tank 18;

[0078] The LEEFT reactor 6 is further connected to the nanofiltration integrated device 14 through the water inlet pipeline. The nanofiltration membrane in the nanofiltration integrated device 14 is a Dow NF 270-400 / 34i commercial nanofiltration membrane. The inlet pH range is 3 to 10, and the maximum operating pressure is 2.5 MPa. The nanofiltration integrated device 14 deeply treats the raw water to produce clear water and concentrated water, which are stored in the production water tank 18 and the concentrated water tank 17 respectively. The nanofiltration membrane in the nanofiltration integrated device 14 adopts a three-stage series operation mode. The concentrated water of the previous stage is used as the inlet water of the next stage. The three stages of produced water are merged, with a total of 3 membrane modules, and the total membrane area is 120.0 m 2 , using Dow NF 270-400 / 34i commercial nanofiltration membrane, the nanofiltration operation recovery rate reached 50%.

[0079] When in use, the permeate outlet flow control valve 15 can also be connected in series to the nanofiltration integrated equipment 14 and the water production tank 18 to control the outlet flow; the concentrate outlet flow control valve 16 can be connected in series to the nanofiltration integrated equipment 14 and the concentrate tank 17 to control the outlet flow.

[0080] Implementation method 5. See Figure 1 This embodiment is described. This embodiment adds a water supply pump 2, a first pressure gauge 4 and a water inlet flow control valve 3 to the local enhanced electric field nanofiltration drinking water treatment device described in Embodiment 4;

[0081] The water supply pump 2 is used to deliver the raw water in the raw water tank 1 to the LEEFT reactor 6;

[0082] The first pressure gauge 4 is connected in series to the LEEFT reactor 6 to detect and display raw water pressure data;

[0083] The water inlet flow control valve 3 is connected in series to the water supply pump 2 and the first pressure gauge 4 to control the water outlet flow.

[0084] In practical application, if Figure 1 As shown, the raw water tank 1 is connected to the LEEFT reactor 6 through a water inlet pipeline, so that the raw water in the raw water tank 1 is transported to the LEEFT reactor 6 through a water feed pump 2, wherein a water inlet flow control valve 3 and a first pressure gauge 4 are respectively installed on the water inlet pipeline, the water inlet flow control valve 3 is used to adjust the water inlet flow rate, and the first pressure gauge 4 is used to detect and display the pressure in the water inlet pipeline to realize the monitoring function.

[0085] Implementation method 6. See Figure 1 This embodiment is described. This embodiment adds a water inlet flow control valve 10, a rotor flowmeter 11, a second pressure gauge 12 and a pressure pump 13 to the local enhanced electric field nanofiltration drinking water treatment device described in Embodiment 5;

[0086] The water inlet flow control valve 10 is connected in series to the water outlet of the LEEFT reactor 6 to control the water outlet flow;

[0087] The rotor flowmeter 11 is connected in series to the water outlet of the water inlet flow control valve 10 to detect and display the water flow;

[0088] The pressure pump 13 is connected in series to the water outlet of the rotor flowmeter 11, and is used to transport raw water to the nanofiltration unit;

[0089] The second pressure gauge 12 is connected in series to the rotor flowmeter 11 and the pressure pump 13 and is used to detect and display the water pressure.

[0090] In practical application, if Figure 1 As shown, the LEEFT reactor 6 is further connected to the nanofiltration integrated device 14 through an inlet pipeline; wherein, an inlet flow control valve 10, a rotor flowmeter 11, a second pressure gauge 12 and a pressure pump 13 are respectively installed on the inlet pipeline; the inlet flow control valve 10 is connected in series to the water outlet of the LEEFT reactor 6 for controlling the outlet water flow; the rotor flowmeter 11 is connected in series to the water outlet of the inlet flow control valve 10 for detecting and displaying the water flow; the pressure pump 13 is connected in series to the water outlet of the rotor flowmeter 11 for conveying raw water to the nanofiltration unit and providing the required pressure for the nanofiltration unit to inlet water; the second pressure gauge 12 is connected in series to the rotor flowmeter 11 and the pressure pump 13 for detecting and displaying the water pressure.

[0091] Implementation method 7. See Figure 1This embodiment is described. This embodiment is based on the local enhanced electric field nanofiltration drinking water treatment device described in Embodiment 6 and adds a PLC control cabinet 19;

[0092] The PLC control cabinet 19 is used to control the drinking water treatment device to perform automated treatment.

[0093] In practical application, if Figure 1 As shown, the entire drinking water treatment system is automatically controlled by an LC control cabinet 19.

[0094] Implementation Method 8. See Figure 2 This embodiment describes a method for treating drinking water with a local enhanced electric field nanofiltration. The method is implemented based on a local enhanced electric field nanofiltration drinking water treatment device according to any one of Embodiments 1 to 7. The method is as follows:

[0095] S1. Use LEEFT unit to remove particles and bacteria from raw water;

[0096] S2. Use nanofiltration unit to deeply treat the raw water after removing particles and bacteria to obtain clean water.

[0097] In practical application, if Figure 2 As shown, a LEEFT unit is used to remove particles and bacteria from the raw water in the raw water tank; a filter unit is used to deeply treat the raw water after the particles and bacteria are removed to obtain clean water, which is stored in a clean water tank.

[0098] Embodiment 9. This embodiment is an example of a method for preparing copper phosphide nanowires Cu3PNWs in the LEEFT unit of step S1 in a local enhanced electric field nanofiltration drinking water treatment method described in embodiment 8;

[0099] The preparation method is:

[0100] S11, washing the copper foam with HCl to remove the oxide layer on the surface of the copper foam;

[0101] S12, washing the foamed copper with deionized water to remove the oxide layer, and then washing with anhydrous ethanol to remove organic matter on the surface of the copper oxide;

[0102] S13, using nitrogen to purge to remove organic copper oxide, and then placing it in sodium hydroxide solution, using chronopotentiometry to obtain Cu(OH)2NWs;

[0103] S14, using sodium phosphite to react with the Cu(OH)2NWs to obtain copper phosphide nanowires Cu3PNWs.

[0104] In actual application, the present embodiment specifically describes the removal of particulate matter and bacteria from raw water in the raw water pool by the LEEFT unit: the LEEFT unit includes a DC power supply 5 and a LEEFT reactor 6; the interior of the LEEFT reactor 6 is composed of an anode 7, a guide net 8 and a cathode 9. The material of the anode 7 and the cathode 9 is copper phosphide nanowires Cu3PNWs, which remove suspended particulate matter in the raw water under the action of aperture screening; the Cu3PNWs surface nanowires also amplify the 1-2.0V voltage provided by the DC power supply to thousands of volts through the local enhanced electric field effect, exceeding the breakdown threshold of the transmembrane potential of the microorganism, thereby inducing an electroporation effect, causing irreversible damage to the microorganisms and bacteria, and then leading to the death of the microorganisms and bacteria.

[0105] The preparation method of copper phosphide nanowires Cu3PNWs is as follows:

[0106] Step 1, washing the copper foam with 0.1-1.0M HCl for 1-30 minutes to remove the oxide layer on the surface of the copper foam;

[0107] Step 2, washing with deionized water for 5 to 20 minutes, and then washing with anhydrous ethanol for 2 to 20 minutes to remove organic matter on the surface of the foam copper;

[0108] Step 3: After purging with 1 bar compressed nitrogen for 1 to 5 minutes, place in 3.0 M sodium hydroxide solution and use chronopotentiometry with a fixed current density of 1.5 to 5 mA / cm 2 , electrochemical anodization for 15 to 30 minutes, the color of the copper foam changed from reddish brown to blue, and Cu(OH)2NWs were obtained;

[0109] Step 4: Place excess sodium phosphite in the center of the tube furnace, flush with argon for 10 to 15 minutes, raise the temperature of the tube furnace to 300°C, place Cu(OH)2NWs at 120°C downstream of the tube furnace, and cool to room temperature in an argon atmosphere after 90 to 120 minutes. The electrode color changes from blue to black, and copper phosphide nanowires Cu3PNWs are obtained.

[0110] Embodiment 10. This embodiment is an example of the nanofiltration unit in step S2 of the local enhanced electric field nanofiltration drinking water treatment method described in Embodiment 8;

[0111] The nanofiltration unit adopts a three-stage series operation mode, the concentrated water from the previous stage of nanofiltration is used as the inlet water for the next stage, the three stages of produced water are merged, and the concentrated water is repeatedly treated.

[0112] In practical application, this embodiment adopts a nanofiltration unit to deeply treat the raw water after removing particles and bacteria to obtain clean water. Specifically, the nanofiltration membrane in the nanofiltration unit adopts a three-stage operation mode in series, and the concentrated water of the previous stage is used as the effluent of the next stage. The 3-stage water production is merged, with a total of 3 membrane modules, and the total membrane area is 120.0m 2 , using Dow NF 270-400 / 34i commercial nanofiltration membrane, the nanofiltration operation recovery rate reached 50%.

[0113] Implementation method 11. See Figure 3 and Figure 4 This embodiment is described. This embodiment is a verification description of the drinking water in Suzhou, Jiangsu Province, China, using a local enhanced electric field nanofiltration drinking water treatment device described in any one of Embodiments 1 to 7:

[0114] Step 1: Use Yangtze River water as raw water, and pre-treat it through the LEEFT unit to preliminarily remove particulate matter and bacteria in the raw water. The specific process is that the raw water enters the LEEFT reactor in the LEEFT unit through the water supply pipe, and the suspended particles are removed under the pore screening effect of the foam copper. After the anode and cathode of the foam copper are connected to the DC power supply, the Cu3PNWs surface nanowires amplify the 1-2.0V voltage provided by the DC power supply to thousands of volts through the local enhanced electric field, exceeding the breakdown threshold of the microbial transmembrane potential, thereby inducing the electroporation effect, causing irreversible damage to microorganisms and bacteria, and then leading to the death of microorganisms and bacteria. Among them, the inactivation efficiency of Escherichia coli under different operating times is as follows: Figure 3 As shown, it can be seen that the survival rate of E. coli gradually decreases with the increase of time, which verifies that the LEEFT unit can effectively remove bacteria in the raw water. The LEEFT unit has a high disinfection efficiency>6.0log removal rate, and no bacterial microorganisms are detected in the effluent water.

[0115] Step 2: The effluent from the LEEFT unit is deeply treated by the nanofiltration integrated process in the nanofiltration unit to improve the effluent quality. Among them, the membrane components in the nanofiltration integrated process have the following requirements on the operating environment: Figure 4 shown.

[0116] The water inlet flow rate in step 1 is controlled to be 15-30 mL / min, and a guide net is used to separate the positive and negative electrodes to prevent short circuit of the loop.

[0117] Among them, the LEEFT unit in step 1 acts as a security filter to ensure that the SDI value of the NF inlet water is smaller than the SDI value of the NF membrane max=5 limit. SDI value is considered one of the important parameters of nanofiltration water inlet index. It reflects the content of particles, colloids and other substances in the water that can block the membrane surface and membrane pores. It is the main parameter for testing whether the effluent of the pre-membrane pretreatment system meets the NF water inlet requirements. It is crucial to the operating life of the membrane filtration system.

[0118] The nanofiltration membrane described in step 2 adopts a three-stage operation mode in series. The concentrated water from the first stage of nanofiltration is used as the effluent from the next stage. The three stages of water production are combined, with a total of three membrane modules and a total membrane area of ​​120m 2 , using Dow NF 270-400 / 34i commercial nanofiltration membrane, the nanofiltration operation recovery rate was 50%.

[0119] Among them, for the NF membrane unit in step 2, in addition to regular water quality testing, the main monitoring parameters of the entire system operation also include water pressure, water volume and temperature.

[0120] Among them, in step 2, the first stage of nanofiltration is easily blocked due to humus and front-end water pollution, so the chemical cleaning is divided into the first, second and third stages. In winter when the water temperature is low, the membrane flux decays, and the concentration rate of the concentrated water side increases, which makes the third stage easy to block, so it is adjusted to the first, second and third stages for flushing.

[0121] During long-term continuous operation, the turbidity of the Yangtze River raw water is about 4-10 NTU, and the turbidity of the nanofiltration produced water is stable at less than 0.1 NTU. From the above results, it can be seen that the drinking water treatment device described in this embodiment has a significant effect on removing turbidity in drinking water in Suzhou area.

[0122] During the long-term operation, the TOC concentration of the raw water was 5.74 mg / L, the TOC concentration of the nanofiltration effluent of the blank operation group was 1.64 mg / L, and the TOC removal rate was 71.4%; after treatment with the LEEFT-nanofiltration combined process, the TOC concentration was 0.23 mg / L, and the TOC removal rate was as high as 96.1%. This shows that the addition of the LEEFT process has improved the TOC removal rate of the nanofiltration process.

[0123] During the long-term continuous operation, the initial membrane flux of the blank operation group was 6.88 L / (h·m 2 ), the steady-state membrane flux is 4.47 L / (h·m 2 ), membrane specific flux is 0.65, and membrane fouling resistance is 10.2×10 14 m -1 ; Under LEEFT pretreatment conditions, the initial membrane flux was about 6.72L / (h·m 2 ), the steady-state membrane flux is 5.51 L / (h·m 2 ), membrane specific flux is 0.82, and membrane fouling resistance is 6.8×10 14 m -1, membrane fouling was reduced by 33.3%.

[0124] To sum up, the locally enhanced electric field nanofiltration drinking water treatment device described in this embodiment adopts the LEEFT unit to remove particulate matter and bacteria in the raw water, wherein the LEEFT unit, as an electrochemical disinfection method, can avoid damage to the nanofiltration membrane by traditional disinfectants; the Cu3PNWs in the LEEFT unit can remove suspended particulate matter through physical screening and alleviate membrane pollution; it has high disinfection efficiency, high water flux, and the hydraulic retention time can be controlled within 3 seconds; it also has the advantages of low energy consumption and applied voltage as low as 1.0~2.0V, which makes the locally enhanced electric field nanofiltration drinking water treatment device described in this embodiment have the characteristics of easy operation, simple design, small footprint and stable operation.

[0125] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0126] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0127] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may be subject to various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A local enhanced electric field nanofiltration drinking water treatment method, the method is implemented based on a local enhanced electric field nanofiltration drinking water treatment device, characterized in that: The device comprises a raw water tank (1), a LEEFT unit and a nanofiltration unit; The raw water tank (1) is used to deliver raw water to the LEEFT unit; The LEEFT unit is used to remove particles and bacteria from raw water, and to deliver the raw water after the particles and bacteria are removed to the nanofiltration unit; The LEEFT unit comprises a DC power supply (5) and a LEEFT reactor (6); The LEEFT reactor (6) comprises an anode (7), a flow guide net (8) and a cathode (9); The flow guide net (8) is used to isolate the anode (7) and the cathode (9); The DC power supply (5) is used to provide a DC voltage to the anode (7) and the cathode (9); The DC voltage is 1-2V; The anode (7) and the cathode (9) are used to remove particles in the raw water, and are also used to amplify the DC voltage to thousands of volts through the local enhanced electric field to remove bacteria in the raw water, and to transport the raw water after the particles and bacteria are removed to the nanofiltration unit; The nanofiltration unit is used to deeply process raw water into clear water and concentrated water, and is also used to repeatedly process the concentrated water; The materials of the anode (7) and cathode (9) are both copper phosphide nanowires Cu3PNWs; The preparation method of the copper phosphide nanowires Cu3PNWs is as follows: The copper foam is washed with HCl to remove the oxide layer on the surface of the copper foam; The foamed copper is washed with deionized water to remove the oxide layer, and then washed with anhydrous ethanol to remove organic matter on the surface of the copper oxide; The copper oxide of organic matter was removed by nitrogen purging, and then placed in sodium hydroxide solution and the Cu(OH)2NWs were prepared by chronopotentiometry. Sodium phosphite is used to react with the Cu(OH)2NWs to obtain copper phosphide nanowires Cu3PNWs; The drinking water treatment method is: S1. Use LEEFT unit to remove particles and bacteria from raw water; S2. Use nanofiltration unit to deeply treat the raw water after removing particles and bacteria to obtain clean water.

2. A method for treating drinking water by locally enhanced electric field nanofiltration according to claim 1, characterized in that: The surface area of ​​the flow guide net (8) is greater than the areas of the anode (7) and the cathode (9).

3. A method for treating drinking water by locally enhanced electric field nanofiltration according to claim 2, characterized in that: The nanofiltration unit comprises a nanofiltration integrated device (14), a permeate outlet flow control valve (15), a concentrate outlet flow control valve (16), a concentrate tank (17) and a production water tank (18); The nanofiltration integrated device (14) is used to perform deep treatment on raw water and deliver the treated clean water to the water production tank (18), and is also used to deliver the treated concentrated water to the concentrated water tank (17), and is also used to repeatedly treat the concentrated water; The permeate outlet flow control valve (15) is connected in series to the nanofiltration integrated device (14) and the water production tank (18) to control the outlet flow rate; The concentrate outlet flow control valve (16) is connected in series to the nanofiltration integrated device (14) and the concentrate tank (17) to control the outlet flow.

4. A method for treating drinking water by locally enhanced electric field nanofiltration according to claim 3, characterized in that: The device also includes a water supply pump (2), a first pressure gauge (4) and a first water inlet flow control valve (3); The water supply pump (2) is used to transport the raw water in the raw water tank (1) to the LEEFT reactor (6); The first pressure gauge (4) is connected in series to the LEEFT reactor (6) and is used to detect and display raw water pressure data; The first water inlet flow control valve (3) is connected in series to the water supply pump (2) and the first pressure gauge (4) and is used to control the water outlet flow.

5. A method for treating drinking water by locally enhanced electric field nanofiltration according to claim 4, characterized in that: The device also includes a second water inlet flow control valve (10), a rotor flow meter (11), a second pressure gauge (12) and a pressure pump (13); The second water inlet flow control valve (10) is connected in series to the water outlet of the LEEFT reactor (6) to control the water outlet flow; The rotor flowmeter (11) is connected in series to the water outlet of the second water inlet flow control valve (10) and is used to detect and display the water flow rate; The pressure pump (13) is connected in series to the water outlet of the rotor flowmeter (11) and is used to transport raw water to the nanofiltration unit; The second pressure gauge (12) is connected in series to the rotor flow meter (11) and the pressure pump (13) and is used to detect and display the water pressure.

6. The method for treating drinking water by locally enhanced electric field nanofiltration according to claim 1, characterized in that: The device also includes a PLC control cabinet (19); The PLC control cabinet (19) is used to control the drinking water treatment device to perform automated treatment.

7. The method for treating drinking water by locally enhanced electric field nanofiltration according to claim 1, characterized in that: The nanofiltration unit in step S2 adopts a three-stage operation mode in series, the concentrated water from the previous stage of nanofiltration is used as the influent water for the next stage, the three stages of produced water are merged, and the concentrated water is repeatedly treated.

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