A few drugs self-regulating nanofiltration coupling system and method of use

Abstract

The application relates to a few-drug self-regulation type nanofiltration coupling system and a use method, and belongs to the technical field of water treatment. The application solves the problems of high chemical agent dependence, high operation energy consumption and high maintenance demand of the existing nanofiltration core membrane water treatment technology. The application comprises a water inlet tank, a drop water aeration tower, a self-driven ecological membrane ultrafiltration, a nanofiltration water inlet tank, a nanofiltration membrane assembly, a nanofiltration water tank, an ion exchange membrane electrolysis reactor, an alkali liquid storage tank, an acid liquid storage tank and a salt water tank. The raw water inlet tank, the drop water aeration tower, the self-driven ecological membrane ultrafiltration, the nanofiltration water inlet tank, the nanofiltration membrane assembly and the water tank are sequentially connected to form a filtration system. The concentrated water interface of the nanofiltration membrane assembly, a concentrated water discharge pipe and a concentrated water return pipe are sequentially connected to form a concentrated water treatment system. The salt water tank, the ion exchange membrane electrolysis reactor, the alkali liquid storage tank and the acid liquid storage tank form an assembly cleaning system. The application can self-detect and predict indexes, and self-regulate and periodically clean without adding other agents.

Description

TECHNICAL FIELD

[0001] The application relates to a few-drug self-regulation type nanofiltration coupling system and a use method, and belongs to the technical field of water treatment. BACKGROUND

[0002] Nanofiltration can simultaneously remove dissolved salts, emerging pollutants, small-molecule natural organic matter, pathogenic microorganisms and colloids in water, and has been widely used in the field of surface water and groundwater purification with poor water quality. However, during the operation of nanofiltration, microscopic processes such as inorganic scaling, microbial breeding and organic adsorption occur, forming complex membrane fouling and reducing the stability of membrane flux. In order to alleviate the complex membrane fouling, chemical agents such as scale inhibitors and biological inhibitors are often added during the operation of nanofiltration to achieve high-flux operation and high-recovery-rate filtration. However, the large amount of chemical agents brings difficulties to the treatment and discharge of nanofiltration concentrated water, and also leads to complex operation and management work, and the excessive dependence on chemical agents is one of the key problems in the popularization and application of nanofiltration. In addition, low-pressure nanofiltration is a commonly used nanofiltration operation mode, which requires a driving pressure of 0.6-1.0 MPa. Compared with processes such as ultrafiltration, the water production energy consumption is still high, and the equipment requirement is high. SUMMARY

[0003] The application is to solve the problems of high dependence on chemical agents, high operation energy consumption and high maintenance demand of the existing nanofiltration-based membrane water treatment technology, and further provides a few-drug self-regulation type nanofiltration coupling system and a use method.

[0004] The technical scheme adopted by the application to solve the above technical problems is:

[0005] A few-drug self-regulation type nanofiltration coupling system, comprising a water inlet tank, a drop water aeration tower, a self-driven ecological membrane ultrafiltration device, a nanofiltration water inlet tank, a nanofiltration membrane assembly, a nanofiltration water production tank, an ion exchange membrane electrolysis reactor, an alkali liquid storage tank, an acid liquid storage tank and a salt water tank, wherein,

[0006] The water inlet tank, the self-driven ecological membrane ultrafiltration device, the nanofiltration water inlet tank, the nanofiltration membrane assembly and the nanofiltration water production tank are sequentially connected by pipelines, and an initial water discharge pipe is further connected to a water outlet pipeline of the nanofiltration membrane assembly;

[0007] A concentrated water discharge pipe is connected to a concentrated water interface of the nanofiltration membrane assembly, a concentrated water return pipe is connected to the concentrated water discharge pipe, and the concentrated water return pipe is connected to a water inlet end of the nanofiltration membrane assembly;

[0008] The salt water tank is connected to the cathode chamber and the anode chamber of the ion exchange membrane electrolysis reactor through pipelines, the cathode chamber of the ion exchange membrane electrolysis reactor is connected to the alkali liquid storage tank through a pipeline, the anode chamber of the ion exchange membrane electrolysis reactor is connected to the acid liquid storage tank through a pipeline, the alkali liquid storage tank and the acid liquid storage tank are respectively connected to the input end of the cleaning pressurizing pump through pipelines, the output end of the cleaning pressurizing pump is connected to the water inlet end of the nanofiltration membrane assembly through a pipeline, the concentrated water interface of the nanofiltration membrane assembly is respectively connected to the alkali liquid storage tank and the acid liquid storage tank through pipelines, the alkali liquid storage tank is connected with a cleaning alkali liquid discharge pipe, and the acid liquid storage tank is connected with a cleaning acid liquid discharge pipe.

[0009] Valves are arranged on each pipeline to control the opening and closing of the pipeline.

[0010] Further, the driving pressure of the nanofiltration membrane is between 0.2 MPa and 0.4 MPa.

[0011] Further, a medium-pressure ultraviolet dechlorination device is arranged on the connecting pipeline between the anode chamber of the ion exchange membrane electrolysis reactor and the acid liquid storage tank.

[0012] Further, the nanofiltration membrane assembly is a disc tube nanofiltration membrane assembly.

[0013] Further, a water inlet pump of the aerator is arranged on the connecting pipeline between the water inlet tank and the drop water aerator, a nanofiltration water inlet pump is arranged on the connecting pipeline between the nanofiltration water inlet tank and the nanofiltration membrane assembly, and a nanofiltration water inlet pump is arranged on the connecting pipeline between the salt water tank and the ion exchange membrane electrolysis reactor.

[0014] Further, a nanofiltration concentrated water discharge valve is arranged on the concentrated water discharge pipe, and a nanofiltration concentrated water return valve is arranged on the concentrated water return pipe.

[0015] Further, a float valve is arranged on the drop water aerator.

[0016] Further, the pore size of the self-driven ecological membrane ultrafiltration is 0.03 μm.

[0017] A use method of the above-mentioned few-drug self-regulation nanofiltration coupling system, including a water production process, a concentrated water treatment process and an assembly cleaning process, wherein,

[0018] The water production process is that raw water passes through the drop water aerator, the self-driven ecological membrane ultrafiltration, the nanofiltration water inlet tank and the nanofiltration membrane assembly in sequence from the water inlet tank, and nanofiltration water and nanofiltration concentrated water are obtained, wherein the nanofiltration water enters the nanofiltration water tank, and the nanofiltration concentrated water enters the concentrated water treatment process.

[0019] The concentrated water treatment process is that the nanofiltration concentrated water is treated by the alkali liquid storage tank and the acid liquid storage tank.

[0020] The concentrated water leaving the nanofiltration membrane assembly in the water production process is partially discharged through a concentrated water discharge pipe, and the remaining concentrated water is returned to the nanofiltration membrane assembly for purification through a concentrated water return pipe;

[0021] The component cleaning process comprises the following steps:

[0022] Step one, cleaning solution generation: water in the salt water tank flows into the cathode chamber and the anode chamber of the ion exchange membrane electrolysis reactor, and after electrolysis, the acid and alkali solutions are discharged into the acid solution storage tank and the alkali solution storage tank, respectively;

[0023] Step two, low-flow cleaning: the original water is replaced by the cleaning pressure pump at a low cleaning solution pressure;

[0024] Step three, circulation: the cleaning solution enters the nanofiltration membrane assembly from the raw water inlet, and the valve on the connecting pipeline between the nanofiltration membrane assembly and the nanofiltration water inlet tank is in the closed state, and the cleaning solution is circulated back to the corresponding acid solution storage tank and alkali solution storage tank and the temperature of the cleaning solution is kept constant;

[0025] Step four, soaking: stop the cleaning pressure pump and let the membrane element be completely soaked in the cleaning solution;

[0026] Step five, high-flow cleaning: high-flow circulating cleaning solution is used, and the pollutants are washed away by the cleaning solution;

[0027] Step six, flushing: the residual cleaning solution in the nanofiltration system is flushed by using the pretreated qualified produced water;

[0028] Step seven, restart the system: after the cleaning is completed, the system is restarted.

[0029] Further, the cleaning condition is that the standardized pressure difference between the inlet water and the concentrated water is increased by 15% or the system is continuously operated for 3-5 months.

[0030] Compared with the prior art, the present application has the following effects:

[0031] The present application improves the recovery rate of drinking water deep treatment, and effectively reduces the secondary pollution of concentrated water discharge;

[0032] By pre-configuring a certain concentration of salt solution, the ion exchange membrane electrolysis device generates acid and alkali solutions without adding other reagents, effectively reducing the maintenance requirements of the nanofiltration system and reducing the operating energy consumption;

[0033] The present application can self-detect and predict indicators, self-regulate and periodically clean, does not need to add other reagents, and realizes a divalent salt removal rate of more than 60%, effectively reducing the maintenance requirements of the nanofiltration system, reducing the difficulty of nanofiltration concentrated water treatment, having good environmental benefits, high economic benefits, and being suitable for village water supply and urban water supply with high concentrated water discharge requirements. BRIEF DESCRIPTION OF DRAWINGS

[0034] Fig. 1 The system flow diagram of the present application;

[0035] Fig. 2 The salt removal effect diagram using the system of the present application, when the operating pressure of the nanofiltration membrane assembly is 0.2-0.4 MPa, figure a) shows that the removal rate of calcium ions is 85%-97% and the removal rate of sulfate ions is 95%-99% when operating for 30 min; figure b) shows that the removal rate of calcium ions is 60%-66% and the removal rate of sulfate ions is 75%-96% when operating for 12 h. DETAILED DESCRIPTION

[0036] Specific embodiment one: combined Figs. 1-2 In this embodiment, a few-drug self-regulating nanofiltration coupling system includes raw water inlet tank 1, drop water aeration tower 2, self-driven ecological membrane ultrafiltration 3, nanofiltration inlet tank 4, nanofiltration membrane assembly 5, nanofiltration water tank 6, ion exchange membrane electrolytic reactor, alkali storage tank 10, acid storage tank 11, and salt water tank 14, wherein,

[0037] Raw water inlet tank 1, self-driven ecological membrane ultrafiltration 3, nanofiltration inlet tank 4, nanofiltration membrane assembly 5, and nanofiltration water tank 6 are sequentially connected by pipelines, and an initial water discharge pipe 15 is further connected to the water outlet pipeline of the nanofiltration membrane assembly 5;

[0038] The concentrated water interface of the nanofiltration membrane assembly 5 is connected by a concentrated water discharge pipe 31, and the concentrated water discharge pipe is connected by a concentrated water return pipe 32, and the concentrated water return pipe is connected to the water inlet end of the nanofiltration membrane assembly 5;

[0039] The salt water tank 14 is connected by pipelines to the cathode chamber 7 and the anode chamber 8 of the ion exchange membrane electrolytic reactor, respectively, the cathode chamber 7 of the ion exchange membrane electrolytic reactor is connected by a pipeline to the alkali storage tank 10, the anode chamber 8 of the ion exchange membrane electrolytic reactor is connected by a pipeline to the acid storage tank 11, the alkali storage tank 10 and the acid storage tank 11 are respectively connected by pipelines to the input end of the cleaning pressure pump 17, the output end of the cleaning pressure pump 17 is connected by a pipeline to the water inlet end of the nanofiltration membrane assembly 5, the concentrated water interface of the nanofiltration membrane assembly 5 is connected by pipelines to the alkali storage tank 10 and the acid storage tank 11, respectively, the alkali storage tank 10 is connected by a cleaning alkali discharge pipe 18, and the acid storage tank 11 is connected by a cleaning acid discharge pipe 19;

[0040] Valves are provided on each pipeline to control the opening and closing of the pipeline.

[0041] The raw water inlet tank 1, the drop water aeration tower 2, the self-driven ecological membrane ultrafiltration 3, the nanofiltration inlet tank 4, the nanofiltration membrane assembly 5, and the water tank are sequentially connected to form a filtration system.

[0042] The concentrated water interface of the nanofiltration membrane assembly 5, the concentrated water discharge pipe 31 and the concentrated water return pipe 32 are sequentially connected to form a concentrated water treatment system.

[0043] The component cleaning system is formed by the brine tank 14, the ion exchange membrane electrolysis reactor, the alkali storage tank 10 and the acid liquid storage tank 11. The nanofiltration membrane assembly 5 is subjected to chemical cleaning such as alkali washing and acid washing through the component cleaning system, and the cleaning condition is that the standardized pressure difference between the water inlet and the concentrated water is increased by 15% or the continuous operation reaches 3-5 months.

[0044] The primary water discharge pipe 15 is provided with a primary water discharge valve 22. In this way, the primary water discharge valve 22 and the primary water discharge pipe 15 are designed to facilitate the separate discharge of primary water. After cleaning, the primary water is discharged for more than 10 minutes or until the system is normally started and the water is clear.

[0045] The drop water aeration tower 2 preferably adopts a batten aeration tower, the number of batten layers is 4-6, the interlayer clearance is 400-600 mm, and preferably the number of batten layers is 5 and the interlayer clearance is 500 mm.

[0046] The connecting pipeline between the nanofiltration water inlet tank 4 and the nanofiltration membrane assembly 5 is provided with a pressure sensor 24 for monitoring the pressure change in the nanofiltration membrane assembly 5. A valve is arranged on the connecting pipeline between the nanofiltration water inlet tank 4 and the nanofiltration membrane assembly 5 to control the on-off.

[0047] The cathode chamber 7 of the ion exchange membrane electrolysis reactor and the anode chamber 8 of the ion exchange membrane electrolysis reactor are separated by an ion exchange membrane and an ion exchange membrane partition plate.

[0048] The water production pipeline of the nanofiltration membrane assembly 5 is communicated with the water inlet pipeline of the nanofiltration water tank 6, and a valve is arranged on the water production pipeline of the nanofiltration membrane assembly 5 and the water inlet pipeline of the nanofiltration water tank 6 respectively to control the nanofiltration membrane assembly 5 water discharge.

[0049] A valve is arranged on the water outlet pipeline of the brine tank 14 to facilitate the control of the water outlet of the brine tank 14.

[0050] The pipeline between the cathode chamber 7 of the ion exchange membrane electrolysis reactor and the alkali storage tank 10 is an alkali channel, and a valve is arranged thereon; the pipeline between the anode chamber 8 of the ion exchange membrane electrolysis reactor and the acid liquid storage tank 11 is an acid channel, and a valve is arranged thereon.

[0051] A cleaning control valve is arranged on the connecting pipeline between the alkali liquid storage tank 10 and the cleaning pressurizing pump 17, on the connecting pipeline between the acid liquid storage tank 11 and the cleaning pressurizing pump 17, and on the connecting pipeline between the cleaning pressurizing pump 17 and the nanofiltration membrane assembly 5. The cleaning water is circulated from the concentrated water interface of the nanofiltration membrane assembly 5 to the alkali liquid storage tank 10 and the acid liquid storage tank 11. The cleaning alkali liquid discharge pipe 18 and the cleaning acid liquid discharge pipe 19 are used for discharging the cleaning waste water, and cleaning liquid discharge control valves are arranged on the cleaning alkali liquid discharge pipe 18 and the cleaning acid liquid discharge pipe 19, respectively.

[0052] The driving pressure of the nanofiltration membrane is between 0.2 MPa and 0.4 MPa. In this way, the nanofiltration membrane technology can effectively remove various pollutants in water, including organic matter and part of inorganic pollutants. The driving pressure of the nanofiltration membrane is between 0.2 MPa and 0.4 MPa, the nanofiltration membrane is operated in an ultra-low pressure mode, the occurrence mode of the nanofiltration membrane pollution is changed, the cleaning difficulty is effectively reduced, the cleaning frequency is reduced, the water production energy consumption is effectively reduced while the water production meets the standard, and the self-driving ecological membrane ultrafiltration 3 utilizes the height difference between the drop water aeration tower 2 and the self-driving ecological membrane ultrafiltration 3 to control the membrane filtration pressure, the membrane filtration pressure is 6 kPa, which is much lower than that of the traditional ultrafiltration process, and the self-driving ecological membrane ultrafiltration 3 adopts a pore diameter of 0.03 μm;

[0053] The nanofiltration membrane assembly 5 preferably adopts an operating pressure of 0.2 MPa to 0.4 MPa, and preferably an operating pressure of 0.4 MPa. At this time, the nanofiltration membrane assembly 5 has a sulfate removal rate of 75% to 99% and a calcium ion removal rate of 60% to 97% in the influent water.

[0054] The ion exchange membrane electrolysis reactor electrolyzes brine to generate acid and alkali liquids, the pH of the acid liquid is about 2, and the pH of the alkali liquid is about 12.

[0055] A medium-pressure ultraviolet dechlorination device 26 is connected and arranged on the connecting pipeline between the anode chamber 8 of the ion exchange membrane electrolysis reactor and the acid liquid storage tank 11. In this way, the acid liquid generated by the anode chamber 8 of the ion exchange membrane electrolysis reactor is first treated by the medium-pressure ultraviolet dechlorination device 26 and then delivered to the acid liquid storage tank 11.

[0056] The nanofiltration membrane assembly 5 is a disc tube nanofiltration membrane assembly 5.

[0057] An aeration tower water inlet pump 27 is arranged on the connecting pipeline between the raw water inlet tank 1 and the drop water aeration tower 2, a nanofiltration water inlet pump 28 is arranged on the connecting pipeline between the nanofiltration inlet tank 4 and the nanofiltration membrane assembly 5, and an ion exchange membrane electrolysis water inlet pump 30 is arranged on the connecting pipeline between the brine tank 14 and the ion exchange membrane electrolysis reactor.

[0058] A nanofiltration concentrated water discharge valve is arranged on the concentrated water discharge pipe, and a nanofiltration concentrated water return valve is arranged on the concentrated water return pipe.

[0059] The falling water aeration tower 2 is connected with a float ball valve 23. The water level in the falling water aeration tower 2 is controlled by the float ball valve.

[0060] The pore size of the self-driven ecological membrane ultrafiltration 3 is 0.03 μm.

[0061] A method for using the above-mentioned drug-reduced self-regulating nanofiltration coupling system, including a water production process, a concentrated water treatment process, and a component cleaning process, wherein,

[0062] The water production process is as follows: raw water flows through the falling water aeration tower 2, the self-driven ecological membrane ultrafiltration 3, the nanofiltration water inlet tank 4, and the nanofiltration membrane component 5 in sequence from the raw water inlet tank 1, and nanofiltration water production and nanofiltration concentrated water are obtained, wherein the nanofiltration water production enters the nanofiltration water production tank 6, and the nanofiltration concentrated water enters the concentrated water treatment process; the raw water inlet tank 1 inputs incoming water, which enters the falling water aeration tower 2 for pretreatment to improve the dissolved oxygen, thereby providing sufficient conditions for removing Fe, Mn, and other pollutants in the raw water; the effluent from the falling water aeration tower 2 enters the self-driven ecological membrane ultrafiltration 3, in which particulate matter, colloids, suspended solids, and pathogenic microorganisms are intercepted, the raw water biodegradability is reduced, and the pollution of the disc tube nanofiltration membrane component is reduced; the self-driven ecological membrane ultrafiltration 3 utilizes the height difference between the falling water aeration tower 2 and the self-driven ecological membrane ultrafiltration 3 to control the membrane filtration pressure; the self-driven ecological membrane ultrafiltration 3 can reduce the molecular weight of organic matter, and the solubility of organic matter can alleviate the formation of certain crystalline crystals with thorns on the nanofiltration surface, thereby protecting the nanofiltration membrane; the effluent from the self-driven ecological membrane ultrafiltration 3 is stored in the nanofiltration water inlet tank 4, and then enters the nanofiltration membrane component 5.

[0063] The concentrated water treatment process is as follows:

[0064] In the water production process, a part of the concentrated water that leaves the nanofiltration membrane component 5 is discharged through the concentrated water discharge pipe 31, and the remaining concentrated water is returned into the suction port of the nanofiltration water inlet pump 27 through the concentrated water return pipe 32, and then enters the nanofiltration membrane component 5 again for purification; at this time, the valves on the concentrated water discharge pipe 31, the concentrated water return pipe 32, and the pipeline in the water production process are kept open, and the valves on the connecting pipeline between the nanofiltration membrane component 5 and the alkali storage tank 10 and the acid storage tank 11 are kept closed. The system recovery rate control is realized by the partial return of the concentrated water, and the flow rate in the membrane component is increased, thereby reducing the risk of membrane pollution.

[0065] The component cleaning process includes the following steps:

[0066] Step one, cleaning solution generation: the water in the salt water tank 14 flows into the cathode chamber 7 and the anode chamber 8 of the ion exchange membrane electrolysis reactor, and after electrolysis, the acid and alkali solutions are discharged into the acid storage tank 11 and the alkali storage tank 10, respectively; the pH of the acid cleaning is about 2, and the pH of the alkaline cleaning is about 12.

[0067] Step two, low flow cleaning: the original water is replaced by cleaning pressure pump 17 at low cleaning pressure; the cleaning pressure is appropriate to control the system so that no obvious permeate water is produced, and the purpose is to replace the original water in the element;

[0068] The nanofiltration membrane module 5 can be cleaned with acid or alkali, alone or simultaneously;

[0069] During acid cleaning, the nanofiltration membrane module cleaning control valve on the water suction line of the alkali storage tank 10 is closed, and the nanofiltration membrane module cleaning control valve on the water suction line of the acid storage tank 11 is opened. The acid is pressurized by the cleaning pressure pump 17, flows into the nanofiltration membrane module 5 through the nanofiltration membrane module cleaning control valve, and is input at a low flow rate.

[0070] During alkali cleaning, the nanofiltration membrane module cleaning control valve on the water suction line of the acid storage tank 11 is closed, and the nanofiltration membrane module cleaning control valve on the water suction line of the alkali storage tank 10 is opened. The alkali is pressurized by the cleaning pressure pump 17, flows into the nanofiltration membrane module 5, and is input at a low flow rate.

[0071] Step three, circulation: the cleaning liquid enters the nanofiltration membrane module 5 from the original water inlet, and exits from the concentrated water interface. At this time, the valve on the connecting pipeline between the nanofiltration membrane module 5 and the nanofiltration water inlet tank 4 is in a closed state. The cleaning liquid is circulated back to the corresponding acid storage tank 11 and alkali storage tank 10, and the temperature of the cleaning liquid is kept constant. The circulation process lasts for 30 minutes.

[0072] Step four, soaking: stop the cleaning pressure pump 17, and let the membrane element be completely soaked in the cleaning liquid. The soaking process lasts for more than 1 hour.

[0073] Step five, high flow cleaning: high flow circulation of the cleaning liquid is adopted, and the pollutants are washed away by the cleaning liquid. The high flow water pump circulation process lasts for 30-60 minutes.

[0074] Step six, flushing: the residual cleaning liquid in the nanofiltration system is flushed with pretreated qualified permeate water. The flushing process lasts for 30 minutes.

[0075] Step seven, restart the system: after the cleaning is completed, the system is restarted. The initial permeate water after the restart cannot be discharged into the nanofiltration permeate tank 6, and a separate initial permeate water discharge valve 22 and pipeline are provided.

[0076] The acid and alkali storage tank 10 is provided with a cleaning alkali discharge control valve and a cleaning acid discharge control valve to discharge cleaning waste water.

[0077] The cleaning condition is that the standardized pressure difference between the inlet water and the concentrated water rises by 15% or the system continuously operates for 3-5 months.

Claims

1. A low-drug self-regulating nanofiltration coupling system, characterized in that: The application relates to a water treatment system, which comprises a raw water inlet tank (1), a drop aeration tower (2), a self-driven ecological membrane ultrafiltration device (3), a nanofiltration water inlet tank (4), a nanofiltration membrane assembly (5), a nanofiltration water outlet tank (6), an ion exchange membrane electrolysis reactor, an alkali liquid storage tank (10), an acid liquid storage tank (11) and a salt water tank (14), wherein, The raw water inlet tank (1), the self-driven ecological membrane ultrafiltration device (3), the nanofiltration water inlet tank (4), the nanofiltration membrane assembly (5) and the nanofiltration water outlet tank (6) are sequentially connected through pipelines, and an initial water outlet pipe (15) is further connected to a water outlet pipeline of the nanofiltration membrane assembly (5). A concentrated water discharge pipe (31) is connected to a concentrated water interface of the nanofiltration membrane assembly (5), and a concentrated water return pipe (32) is connected to an inlet end of the nanofiltration membrane assembly (5). The salt water tank (14) is connected to a cathode chamber (7) and an anode chamber (8) of the ion exchange membrane electrolysis reactor through pipelines, the cathode chamber (7) of the ion exchange membrane electrolysis reactor is connected to the alkali liquid storage tank (10) through a pipeline, the anode chamber (8) of the ion exchange membrane electrolysis reactor is connected to the acid liquid storage tank (11) through a pipeline, the alkali liquid storage tank (10) and the acid liquid storage tank (11) are respectively connected to an input end of a cleaning pressure pump (17) through pipelines, an output end of the cleaning pressure pump (17) is connected to the inlet end of the nanofiltration membrane assembly (5) through a pipeline, the concentrated water interface of the nanofiltration membrane assembly (5) is respectively connected to the alkali liquid storage tank (10) and the acid liquid storage tank (11) through pipelines, the alkali liquid storage tank (10) is provided with a cleaning alkali liquid discharge pipe (18), and the acid liquid storage tank (11) is provided with a cleaning acid liquid discharge pipe (19). Valves are arranged on the pipelines to control the opening and closing of the pipelines. The raw water inlet tank (1), the drop aeration tower (2), the self-driven ecological membrane ultrafiltration device (3), the nanofiltration water inlet tank (4), the nanofiltration membrane assembly (5) and the water outlet tank are sequentially connected to form a filtration system. The concentrated water interface, the concentrated water discharge pipe (31) and the concentrated water return pipe (32) of the nanofiltration membrane assembly (5) are sequentially connected to form a concentrated water treatment system. The salt water tank (14), the ion exchange membrane electrolysis reactor, the alkali liquid storage tank (10) and the acid liquid storage tank (11) form a component cleaning system. The initial water outlet pipe (15) is provided with an initial water outlet valve (22).

2. The self-regulated nanofiltration coupled system of claim 1, wherein: The driving pressure of the nanofiltration membrane is between 0.2 MPa and 0.4 MPa.

3. The self-regulated nanofiltration system according to claim 1 or 2, wherein: A medium-pressure ultraviolet dechlorination device (26) is arranged on a connecting pipeline between the anode chamber (8) of the ion exchange membrane electrolysis reactor and the acid liquid storage tank (11).

4. The self-regulated nanofiltration coupled system of claim 1, wherein: The nanofiltration membrane assembly (5) is a disc tube type nanofiltration membrane assembly (5).

5. The self-regulated nanofiltration system according to claim 1, 2 or 4, wherein: An aeration tower water inlet pump (27) is arranged on the connecting pipeline between the raw water inlet tank (1) and the drop aeration tower (2), a nanofiltration water inlet pump (28) is arranged on the connecting pipeline between the nanofiltration water inlet tank (4) and the nanofiltration membrane assembly (5), and an ion exchange membrane electrolysis water inlet pump (30) is arranged on the connecting pipeline between the salt water tank (14) and the ion exchange membrane electrolysis reactor.

6. The self-regulated nanofiltration coupled system of claim 1, wherein: A nanofiltration concentrated water discharge valve is arranged on the concentrated water discharge pipe (31), and a nanofiltration concentrated water return valve is arranged on the concentrated water return pipe (32).

7. The self-regulated nanofiltration coupled system of claim 1, 2, 4 or 6, wherein: The drop aeration tower (2) is connected with a float valve (23).

8. The self-regulated nanofiltration coupled system of claim 1, wherein: The aperture of the self-driven ecological membrane ultrafiltration (3) is 0.03 μm.

9. The use of the self-regulated nanofiltration system according to any one of claims 1-8, characterized in that: The method comprises a water production process, a concentrated water treatment process and an assembly cleaning process, wherein, The water production process is that raw water flows from the raw water inlet tank (1) through the drop aeration tower (2), the self-driven ecological membrane ultrafiltration (3), the nanofiltration water inlet tank (4) and the nanofiltration membrane assembly (5) in sequence to obtain nanofiltration water and nanofiltration concentrated water, wherein the nanofiltration water enters the nanofiltration water tank (6), and the nanofiltration concentrated water enters the concentrated water treatment process; The concentrated water treatment process is: The concentrated water leaving the nanofiltration membrane assembly (5) in the water production process is discharged through the concentrated water discharge pipe (31) in part, and the remaining concentrated water is returned through the concentrated water return pipe (32) to enter the nanofiltration membrane assembly (5) again for purification; The assembly cleaning process comprises the following steps: Step one, cleaning liquid generation: water in the salt water tank (14) flows into the cathode chamber (7) and the anode chamber (8) of the ion exchange membrane electrolysis reactor, and after electrolysis, acid and alkali liquids are discharged into the acid liquid storage tank (11) and the alkali liquid storage tank (10) respectively; Step two, low-flow cleaning: the cleaning pressurizing pump (17) is used to replace the raw water at a low cleaning liquid pressure; Step three, circulation: the cleaning liquid enters the nanofiltration membrane assembly (5) from the raw water inlet, and is discharged from the concentrated water interface, at this time, the valve on the connecting pipeline between the nanofiltration membrane assembly (5) and the nanofiltration water inlet tank (4) is in a closed state, the cleaning liquid is circulated back to the corresponding acid liquid storage tank (11) and the alkali liquid storage tank (10), and the temperature of the cleaning liquid is kept constant; Step four, soaking: the cleaning pressurizing pump (17) is stopped, and the membrane element is completely soaked in the cleaning liquid; Step five, high-flow cleaning: high-flow circulating cleaning liquid is used, and the pollutants are washed away by the cleaning liquid; Step six, flushing: the residual cleaning liquid in the nanofiltration system is flushed by using pretreated qualified water production; Step seven, restarting the system: after the cleaning is completed, the system is restarted.

10. The method of use of claim 9, wherein: The cleaning condition is that the standardized pressure difference between the inlet water and the concentrated water is increased by 15%, or the system is continuously operated for 3-5 months.

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