Ozone-hydrogen peroxide coupling cleaning method for seawater desalination ultrafiltration membrane

Abstract

The invention discloses an ozone-hydrogen peroxide coupling cleaning method for a sea water desalination ultrafiltration membrane, which comprises the following steps of: adding ozone into a gas washing gas inlet pipe through a compressed ozone gas conveying pipe and a pressure reducing valve, and then entering an ultrafiltration device for cleaning; water and ozone in the ultrafiltration clean water tank are conveyed to the liquid-liquid high-speed mixing pipe through the gas-liquid micro-nano dissolved gas pipe, hydrogen peroxide is added into the liquid-liquid high-speed mixing pipe, and a gas-liquid mixture in the liquid-liquid high-speed mixing pipe enters the ultrafiltration device for backwashing. In the cleaning process, ozone and free radicals with high oxidation potential, which are rapidly generated by coupling reaction of ozone and hydrogen peroxide, are utilized to perform deep cleaning effects of oxidation, erosion, stripping, oxidation, sterilization and the like on algae microorganisms, inorganic suspended matters, attached organic matters and microorganism reproduction mucous membranes on the ultrafiltration surface. The ozone utilization efficiency is improved, the problem of blockage of the ultrafiltration membrane is solved through efficient cleaning, and the strength and the cleaning frequency of subsequent enhanced backwashing and chemical cleaning are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and particularly relates to an ozone-hydrogen peroxide coupling cleaning method for a seawater desalination ultrafiltration membrane. Background Art

[0002] During seawater desalination treatment, the situation of excessive algae is frequently faced. Algae are extremely likely to block the ultrafiltration membrane and even reproduce on the membrane surface to form a viscous adhesion layer. In the case of ineffective cleaning, problems such as a significant decrease in membrane flux and an increase in transmembrane pressure difference will occur, seriously affecting the operation of the ultrafiltration system. In scenarios where seawater quality deteriorates or the nuclear power safety factor requirement is high, achieving the goal of stable water supply for the ultrafiltration system is particularly important. In this context, maintaining a stable efficiency of ultrafiltration membrane treatment depends on a more efficient cleaning method.

[0003] During ultrafiltration operation, air scrubbing and air-water backwashing are carried out every 30 - 60 minutes to relieve membrane fouling. The cleaning generally adopts the method of backwashing with filtered water and compressed air, which can achieve very significant effects in the case of relatively light fouling, but it cannot achieve the expected cleaning effect for stubborn fouling formed by the adhesion of microorganisms such as algae and their secretions. This is mainly because the cleaning mechanism of the existing technology mainly relies on the effects of hydraulic and gas flushing and erosion, and the cleaning effect on the accumulated organic pollutants on the membrane surface is relatively limited. The traditional process can be further relieved by adding chemical agents for enhanced backwashing. Generally, 500 mg / L of NaOH + NaClO or hydrochloric acid is added for enhanced backwashing, and a normal washing is required after the backwashing is completed to restore the normal filtration environment. The frequency of this process is about once a day. In addition, ultrafiltration will also perform chemical cleaning every 3 - 6 months according to the operating conditions, using acids, alkalis and bactericides with a concentration of 2000 mg / L or even higher. Among them, alkalis and bactericides are mainly aimed at organic pollution, and acid washing is aimed at inorganic pollutants such as silicon and calcium carbonate crystals. However, high-concentration acid and alkali washing may damage the structure of the ultrafiltration membrane filaments, and frequent cleaning potentially reduces the potential service life of the ultrafiltration membrane module. Summary of the Invention

[0004] In order to overcome the deficiencies of the existing technology, the purpose of the present invention is to provide an ozone-hydrogen peroxide coupling cleaning method for a seawater desalination ultrafiltration membrane. By adopting ozone and hydrogen peroxide to couple and clean the ultrafiltration membrane, it can efficiently control the reproduction of algae on the membrane surface and backwash the fouling substances on the ultrafiltration membrane, achieving the purpose of daily cleaning the ultrafiltration membrane to maintain the membrane flux. Using this backwashing technology can effectively reduce the frequency and intensity of enhanced backwashing and chemical cleaning, and overall extend the service life of the ultrafiltration membrane.

[0005] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0006] An ozone-hydrogen peroxide coupled cleaning system for a seawater desalination ultrafiltration membrane, comprising an ozone generation unit, an ozone and hydrogen peroxide dosing and reaction unit, a pure gas washing branch unit, an ultrafiltration membrane unit and a tail gas treatment unit;

[0007] The ozone generation unit is connected to the ozone and hydrogen peroxide dosing and reaction unit;

[0008] The ozone and hydrogen peroxide dosing and reaction unit includes an ozone gas supply pipe, a hydrogen peroxide dosing pipe, a gas-liquid micro-nano dissolution pipe, and a liquid-liquid high-speed mixing pipe. The outlet of the ozone generation unit is divided into two paths. One path is connected to the gas-liquid micro-nano dissolution pipe through the ozone gas supply pipe. The gas-liquid micro-nano dissolution pipe, the hydrogen peroxide dosing pipe and the liquid-liquid high-speed mixing pipe are connected. The liquid-liquid high-speed mixing pipe is connected to the ultrafiltration membrane unit; the other path of the outlet of the ozone generation unit is connected to the ultrafiltration membrane unit through the pure gas washing branch unit; the ultrafiltration membrane unit is connected to the tail gas treatment unit.

[0009] Further, it also includes a concentrated water discharge pipe arranged above the ultrafiltration membrane unit and a backwash water discharge pipe arranged at the bottom of the ultrafiltration membrane unit. The concentrated water discharge pipe and the backwash water discharge pipe are connected to the tail gas treatment unit.

[0010] Further, the ozone generation unit includes an air source ozone generator, an air compressor and an ozone compression storage tank. The air source ozone generator is connected to the air compressor, and the air compressor is connected to the ozone compression storage tank.

[0011] Further, the pure gas washing branch unit includes a compressed ozone gas delivery pipe, a pressure reducing valve, a pressure tester, a gas washing controller and a gas washing inlet pipe. The compressed ozone gas delivery pipe is connected to the ultrafiltration membrane unit through the pressure reducing valve, the pressure tester, the gas washing controller and the gas washing inlet pipe.

[0012] Further, the ultrafiltration membrane unit includes a raw water tank, an ultrafiltration inlet pipe and an ultrafiltration device. The raw water tank is connected to the ultrafiltration inlet pipe, the ultrafiltration inlet pipe is connected to the ultrafiltration device. The liquid-liquid high-speed mixing pipe and the gas washing inlet pipe are connected to the ultrafiltration device. An ultrafiltration outlet pipe is also arranged at the top of the ultrafiltration device. The ultrafiltration outlet pipe is connected to an ultrafiltration clean water tank, and the ultrafiltration clean water tank is connected to the gas-liquid micro-nano dissolution pipe.

[0013] An ozone-hydrogen peroxide coupled cleaning method for a seawater desalination ultrafiltration membrane, comprising the following steps:

[0014] 1) Ozone is added to the gas washing inlet pipe through the compressed ozone gas delivery pipe and the pressure reducing valve, and then enters the ultrafiltration device for cleaning;

[0015] 2) The water in the ultrafiltration clean water tank and ozone are transported to the liquid-liquid high-speed mixing pipe through the gas-liquid micro-nano dissolution pipe, and hydrogen peroxide is added into the liquid-liquid high-speed mixing pipe. The gas-liquid mixture in the liquid-liquid high-speed mixing pipe enters the ultrafiltration device for backwashing.

[0016] Furthermore, the ozone dosage Q O3 is controlled by the following formula (1):

[0017] Q O3 = Q s × [C 0 + K P × (C t - C 0 )] (1)

[0018] Q O3 —— The ozone dosage, g / h;

[0019] Q s —— The backwash water flow rate, m 3 / h;

[0020] C 0 —— The target ozone concentration, g / m 3 ;

[0021] K p —— The proportional adjustment coefficient;

[0022] C t —— The ozone concentration measured by the on-line ozone monitoring sensor.

[0023] Furthermore, the target ozone concentration is calculated by the following formula:

[0024]

[0025] k 1 —— The empirical coefficient;

[0026] T 1 —— The time required to adjust the pressure to a constant value, filter the water sample with a 0.45 μm membrane, and initially collect 500 mL of the water sample, s;

[0027] T 2 —— The time required to collect 500 mL of the water sample again after continuous filtration for t minutes, s;

[0028] t —— The time interval between two samplings, s.

[0029] Furthermore, in step 1), the time for entering the ultrafiltration device for cleaning is 5 min, and the outlet pressure of the pressure reducing valve is 0.1 MPa.

[0030] Furthermore, in step 2), the mass ratio of the ozone dosage to the hydrogen peroxide dosage is O 3 : H 2 O 2 = 1:1 to 1:1.2, and the time for the gas-liquid mixture in the high-speed liquid mixing tube to enter the ultrafiltration device for backwashing is 20 min - 30 min.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] The present invention provides a method for coupling ozone and hydrogen peroxide for cleaning an ultrafiltration membrane for seawater desalination. Ozone and hydrogen peroxide are applied to the backwashing process of the ultrafiltration membrane. The methods of ozone gas washing and ozone-hydrogen peroxide coupling backwashing are used to alleviate problems such as algal fouling of the ultrafiltration membrane. The decomposition products of the chemicals are all environmentally friendly substances, which is a brand-new green cleaning method. The present invention gives full play to the highly oxidizing free radicals rapidly generated by the coupling reaction of ozone and hydrogen peroxide, further improving the ozone utilization efficiency. The cleaning process applies the mechanisms of erosion, exfoliation, oxidation, and disinfection of gas and water to deeply clean the ultrafiltration membrane, reducing the frequency and intensity of enhanced backwashing and chemical cleaning, maintaining good membrane flux and transmembrane pressure difference, and prolonging the service life of the membrane.

[0033] Furthermore, the dosing method, dosage, operating procedure, and post-treatment during operation are systematically designed, further improving the cleaning effect and practicality of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a schematic structural diagram of the device of the present invention;

[0035] Figure 2 is a schematic diagram of the principle of the present invention;

[0036] In the figure, 1 is the raw water tank; 2 is the air-source ozone generator; 3 is the air compressor; 4 is the ozone compression storage tank; 5 is the hydrogen peroxide storage tank; 6 is the ultrafiltration inlet pipe; 7 is the ozone gas addition pipe; 8 is the hydrogen peroxide dosing pipe; 9 is the gas-liquid micro-nano dissolution pipe; 10 is the liquid-liquid high-speed mixing pipe; 11 is the automatic control valve; 12 is the ultrafiltration device; 13 is the compressed ozone gas delivery pipe; 14 is the pressure reducing valve; 15 is the pressure tester; 16 is the gas washing controller; 17 is the gas washing inlet pipe; 18 is the concentrated water discharge pipe; 19 is the backwashing water discharge pipe; 20 is the concentrated water discharge trench; 21 is the cleaning water discharge trench; 22 is the ultrafiltration outlet pipe; 23 is the ultrafiltration outlet pipe fitting valve; 24 is the ultrafiltration clean water tank; 25 is the valve; 26 is the backwashing feed pump; 27 is the backwashing pressure and flow measuring device; 28 is the ozone destructor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0038] In addition, an element in the present invention is referred to as "fixed to" or "disposed on" another element, which can be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for illustrative purposes and do not represent the only implementation.

[0039] The standard electrode potential of ozone reaches 2.07V, which is higher than that of chlorine and potassium permanganate. After ozone decomposes, it will produce oxygen and strongly oxidizing single-atom O·, which mainly plays the role of oxidation and sterilization. Using ozone washing or air-water washing is a very green cleaning method, which can effectively reach the membrane surface, shake the membrane filaments to sterilize and erode the sticky biofilm to relieve the fouling of organic matters such as algae on the ultrafiltration membrane. In order to further improve the utilization rate of ozone, adding hydrogen peroxide can greatly enhance the generation of strongly oxidizing hydroxyl HO· to play a role. The chain reaction of ozone and hydrogen peroxide generates hydroxyl radicals through a cyclic path of initiation - transfer - expansion - termination. The main chemical reactions are shown in reaction formulas (1)-(4). Introducing this coupling reaction ensures the effectiveness of ozone cleaning, making the ozone-hydrogen peroxide coupled cleaning of ultrafiltration membranes have strong practical application value.

[0040]

[0041] O 3 +HO 2 - →·O 3 - +HO 2 · (2)

[0042] ·O 3 - +H 2 O→HO·+2O 2 (3)

[0043] HO 2 ·+O 3 →HO·+2O 2 (4)

[0044] Ozone is an easily decomposable substance and is produced and used immediately by an industrial air-source ozone generator. The industrial production and storage technology of hydrogen peroxide is relatively perfect, and the finished product of hydrogen peroxide can be transported to the site for short-term storage and use. The reaction between the two is relatively rapid, and both low concentrations of ozone and hydrogen peroxide are used in the present invention.

[0045] See Figure 1, the ozone-hydrogen peroxide coupling cleaning system of the seawater desalination ultrafiltration membrane used in the cleaning method of the present invention mainly consists of an ozone generation unit, an ozone and hydrogen peroxide dosing reaction unit, a pure gas washing branch unit, an ultrafiltration membrane unit and a tail gas treatment unit.

[0046] The ozone generation unit mainly consists of an air source ozone generator 2, an air compressor 3 and an ozone compression storage tank 4. The air source ozone generator 2 is connected to the air compressor 3, and the air compressor 3 is connected to the ozone compression storage tank 4. The ozone generated by the air source ozone generator 2 is stored in the ozone compression storage tank 4 under the pressure of the air compressor 3 for later use.

[0047] The ozone and hydrogen peroxide dosing reaction unit includes an ozone dosing pipe 7, a hydrogen peroxide dosing pipe 8, a gas-liquid micro-nano dissolution pipe 9, a liquid-liquid high-speed mixing pipe 10, a valve 25, a backwash feed water pump 26 and a backwash pressure and flow measuring device 27. The outlet of the ozone compression storage tank 4 is divided into two paths. One path is connected to the gas-liquid micro-nano dissolution pipe 9 through the ozone dosing pipe. The gas-liquid micro-nano dissolution pipe 9, the hydrogen peroxide dosing pipe 8 and the liquid-liquid high-speed mixing pipe 10 are connected. An automatic control valve 11 is provided on the liquid-liquid high-speed mixing pipe 10, and the liquid-liquid high-speed mixing pipe 10 is connected to the ultrafiltration membrane unit; the other path of the outlet of the ozone compression storage tank 4 is connected to the ultrafiltration membrane unit through the compressed ozone gas transmission pipe 13 via the pure gas washing branch unit.

[0048] The function of the ozone and hydrogen peroxide dosing reaction unit is to complete dosing, backwashing and program control. The concentrated water in the ultrafiltration membrane unit is drained through the concentrated water discharge pipe 18 provided at the upper part of the ultrafiltration membrane unit and the concentrated water discharge trench 20. An ozone destructor 28 is provided between the concentrated water discharge pipe 18 and the concentrated water discharge trench 20. The cleaning water in the ultrafiltration membrane unit is drained through the backwash water discharge pipe 19 provided at the bottom of the ultrafiltration membrane unit and the cleaning water discharge trench 21. An ozone destructor 28 is provided between the backwash water discharge pipe 19 and the cleaning water discharge trench 21. The ozone in the ozone compression storage tank 4 and the hydrogen peroxide in the hydrogen peroxide storage tank 5 are successively added to the backwash pipeline through the gas-liquid micro-nano dissolution pipe 9 and the liquid-liquid high-speed mixing pipe 10, and are mixed evenly under the action of water flow to react. The gas-water mixture after complete reaction is discharged to complete the cleaning.

[0049] The pure gas washing branch unit is used to control the pure ozone gas washing process, and includes a pressure reducing valve 14, a pressure tester 15, a gas washing controller 16 and a gas washing inlet pipe 17. The compressed ozone gas transmission pipe 13 is connected to the ultrafiltration membrane unit through the pressure reducing valve 14, the pressure tester 15, the gas washing controller 16 and the gas washing inlet pipe 17.

[0050] The ultrafiltration membrane unit mainly consists of an ultrafiltration membrane module, a frame and auxiliary facilities, including a raw water tank 1, an ultrafiltration water inlet pipe 6 and an ultrafiltration device 12. The raw water tank 1 is connected to the ultrafiltration water inlet pipe 6, and the ultrafiltration water inlet pipe 6 is connected to the ultrafiltration device 12. The ultrafiltration device 12 includes a membrane module, and the membrane module in the ultrafiltration device 12 needs to be cleaned regularly. The ultrafiltration device 12 is connected to a liquid-liquid high-speed mixing pipe 10. The ultrafiltration device 12 is connected to a gas washing air inlet pipe 17. An ultrafiltration water outlet pipe 22 is also provided at the top of the ultrafiltration device 12, and the ultrafiltration water outlet pipe 22 is connected to an ultrafiltration clean water tank 24 through an ultrafiltration water outlet pipe fitting valve 23.

[0051] The ozone destructor 28 constitutes an exhaust gas treatment unit to prevent the exhaust gas with incomplete reaction from entering the space and causing harm to the operators. The ozone destructor 28 adopts the chemical absorption method. It uses the oxygen reduction reaction to absorb ozone gas. This device is arranged in the form of a gas collecting hood, which is opened during the cleaning process and closed 3 - 5 minutes after the cleaning ends.

[0052] See Figure 2 , the ozone-hydrogen peroxide coupling cleaning method for the seawater desalination ultrafiltration membrane in the present invention includes the following steps:

[0053] Firstly, the ozone in the ozone compression storage tank 3 and the oxygen generated in the reaction are used to act on the membrane filaments in the ultrafiltration device 12, and under the action of inertia, the pollutants are separated from the surface of the ultrafiltration membrane in the ultrafiltration device 12. This is also the most common action mechanism in conventional gas washing. In addition, the present invention can oxidize, erode and exfoliate the sticky biofilm formed by the reproduction of microorganisms and the deposited inorganic suspended matter under the action of O 3 , HO·, O·, O 2 The reproduction phenomenon of algal microorganisms is effectively controlled, and the inorganic suspended matter is more easily washed away from the surface of the membrane by gas and water, so that the ultrafiltration membrane pores are always in a relatively clean state. For the organic matter and microorganisms attached to the ultrafiltration membrane, the main functions of O 3 , HO·, O· are oxidation and sterilization. After oxidation and sterilization, the organic matter and algal microorganisms will also be carried away by the water flow to complete the flushing and cleaning process.

[0054] The generation and dosing methods of ozone and hydrogen peroxide mainly adopt the following two:

[0055] 1) For gas washing, micro-pressurized ozone is directly dosed, and the gas shakes the membrane filaments and instantaneously sterilizes.

[0056] 2) For the mode of ozone and hydrogen peroxide coupled backwashing, it is achieved by the gas-liquid micro-nano dissolved gas pipe 9 and the liquid-liquid high-speed pipe 10. The gas-liquid micro-nano dissolved gas pipe 9 injects ozone into the backwashing water in the form of microbubbles, and the liquid-liquid high-speed pipe 10 realizes the mixing of hydrogen peroxide and ozone microbubbles. The sequence is to first mix ozone with the backwashing water through the gas-liquid micro-nano dissolved gas pipe 9, and then set the liquid-liquid high-speed pipe 10 to realize the mixing of hydrogen peroxide and ozone microbubbles.

[0057] 3) During the air-water washing process, the mass ratio of ozone and hydrogen peroxide dosage is O 3 :H 2 O 2 = 1:1 to 1:1.2, to avoid self-quenching caused by excessive H 2 O 2 . The dosage is controlled by a fully automatic metering pump during this process.

[0058] The ozone dosage Q O3 during air washing is dynamically feedback-controlled by the following formula (1):

[0059] Q O3 = Q s ×[C 0 + K P ×(C t - C 0 )] (1)

[0060] Q O3 ——Ozone dosage (g / h);

[0061] Q s ——Backwashing water flow rate (m 3 / h);

[0062] C 0 ——Target ozone concentration (g / m 3 );

[0063] K p ——Proportional adjustment coefficient, set according to system response, generally set to 0.5 - 1.1;

[0064] C t ——Ozone concentration measured by the on-line ozone monitoring sensor;

[0065] When the water quality data is certain or in the initial stage of operation, the target ozone concentration C 0 usually adopts the empirical value of 1 - 5 mg / L, which can ensure that the residual ozone in the backwashing drainage ≤ 0.1 mg / L. It can not only ensure good oxidation effect but also avoid over-oxidation.

[0066] When the water quality data is complete, the dosage is adjusted by formula (2):

[0067]

[0068] k 1 —— An empirical coefficient, usually taken as 0.1 - 0.3;

[0069] T 1 —— The time (unit: seconds) required to adjust the pressure to a constant value (usually 30 psi, approximately 2.07 bar), filter the water sample with a 0.45 μm membrane, and initially collect 500 mL of the water sample;

[0070] T 2 —— The time (unit: seconds) required to collect another 500 mL of the water sample after continuously filtering for t minutes;

[0071] t —— The interval time between two samplings (usually taken as 15 minutes).

[0072] The cleaning process adopts a program of gas cleaning first and then gas - water cleaning. During operation, the cleaning frequency is reduced to once every 90 minutes. This process is realized by automatic valves and operates with a pulsed cleaning program.

[0073] The specific cleaning process and parameters are as follows:

[0074] 1) The pressure during gas cleaning should not be too high to avoid breaking the membrane filaments. The ozone supplied by the compressed ozone storage tank 4 is decompressed and introduced for cleaning at a pressure of 0.1 MPa, and the cleaning time is 5 minutes.

[0075] 2) The gas - water cleaning time is reduced to 20 - 30 minutes.

[0076] After the entire cleaning process is completed, for subsequent enhanced backwashing and chemical cleaning, the chemical dosing concentration and cleaning frequency can be appropriately reduced according to the operating conditions.

[0077] 1) For enhanced backwashing, generally 300 mg / L of NaOH + NaClO and 400 mg / L of hydrochloric acid are added for backwashing, and the frequency of this process is reduced to once every two days.

[0078] 2) In addition, the ultrafiltration will also be chemically cleaned once every 4 - 12 months according to the operating conditions, using 2000 mg / L of acid - base and bactericide for cleaning.

[0079] The cleaning method in Example 1 includes a gas cleaning process with pure ozone.

[0080] During the air flushing process, the original water tank 1 and the ultrafiltration inlet pipe 6 are closed. The air source ozone generator 2 and the air compressor 3 are turned on 1 hour in advance. The ozone compression storage tank 4 is controlled by the program to open and the compressed ozone gas is transported through the compressed ozone gas delivery pipe 13. The pressure reducing valve 14 is adjusted to control the outlet pressure to be 0.1 MPa. The pressure tester 15 displays the real-time pressure and feeds back to adjust the air flushing controller 16 to ensure that the air flushing pressure is appropriate. The air flushing ozone amount calculated by formula (1) is added to the air flushing inlet pipe 17 and enters from the bottom between the ultrafiltration membrane groups of the ultrafiltration device 12. The concentrated water discharge pipe 18 is kept unobstructed, and the effluent is discharged into the concentrated water discharge trench 20. During this period, it is fully cleaned for 5 minutes. The tail gas is absorbed by the ozone destroyer 28, and the purified gas after absorption is discharged into the atmosphere. After the cleaning is completed, the air flushing controller 16 automatically closes the intake valve and the ozone generating device 2, and one cleaning cycle ends, preparing for the next operation process.

[0081] The cleaning method of Example 2 includes the air-water flushing process.

[0082] The externally transported hydrogen peroxide is connected to the hydrogen peroxide storage tank 5 in the workshop, and the storage time does not exceed 48 hours. The air source ozone generator 2 and the air compressor 3 are turned on 1 hour in advance. After the ozone gas and the hydrogen peroxide material are prepared, first open the valve 25 connected to the ultrafiltration clean water tank 24, the backwash feed pump 26, the backwash pressure and flow measurement device 27, then open the switch of the ozone addition pipe 7 where the air-liquid micro-nano dissolution pipe 9 is located, and finally open the valve of the hydrogen peroxide dosing pipe 8 of the pipeline where the liquid-liquid high-speed mixing pipe 10 is located. The backwash program is started according to the ultrafiltration backwash sequence. At this time, the ultrafiltration outlet pipe 22 is controlled to be closed by the ultrafiltration outlet pipe fitting valve 23, and the backwash effluent is discharged from the backwash water discharge pipe 19 into the cleaning water discharge trench 21. The air-water flushing time is controlled to be 20 min - 30 min. The tail gas is absorbed by the ozone destroyer 28, and the purified gas after absorption is discharged into the atmosphere.

[0083] In Example 3, the algae and microorganisms reproduce severely. The cleaning method includes a process of first performing air flushing and then air-water flushing.

[0084] The air washing process is specifically as follows: First, shut down the original water tank 1 and the ultrafiltration inlet pipe 6 to stop water inlet filtration. Start the air source ozone generator 2 and the air compressor 3 one hour in advance, control the ozone compression storage tank 4 to complete pressure accumulation, automatically open the valve of the compressed ozone gas delivery pipe 13 by the automatic program, automatically adjust the pressure reducing valve 14 to control the outlet pressure to be about 0.1 MPa, check whether the real-time pressure shown by the pressure tester 15 is normal, and feedback and adjust the air washing controller 16 to ensure that the air washing pressure is always appropriate. Keep a certain amount of ozone intake during air washing. The air washing inlet pipe 17 enters from the bottom of the ultrafiltration membrane of the ultrafiltration device 12, keep the concentrated water discharge pipe 18 unobstructed, and discharge the water to the concentrated water discharge trench 20. Thoroughly wash for 5 minutes during this period. After the washing is completed, the air washing controller 16 automatically closes the inlet valve of this pipeline but does not close the ozone generating device 2. The externally transported hydrogen peroxide is connected to the hydrogen peroxide storage tank 5. After the ozone gas and hydrogen peroxide materials are prepared, first open the valve 25 connected to the ultrafiltration clean water tank 24, the backwashing feed water pump 26, the backwashing pressure and flow measuring device 27, then open the switch of the ozone adding pipe 7 where the gas-liquid micro-nano dissolution pipe 9 is located, and finally open the hydrogen peroxide dosing pipe 8 of the pipeline where the liquid-liquid high-speed mixing pipe 10 is located. Start the backwashing program according to the ultrafiltration backwashing sequence. At this time, control the ultrafiltration outlet pipe 22 to close by using the ultrafiltration outlet pipe fitting valve 23, and discharge the backwashing water from the backwashing water discharge pipe 19 to the cleaning water discharge trench 21. Control the air-water washing time to 30 minutes, and purify the tail gas with the ozone destroyer 28. Discharge the purified gas after absorption into the atmosphere. After the cleaning is completed, close the backwashing valve. The transmembrane pressure difference and membrane flux are restored, and then open the ultrafiltration inlet pipe 6 to supply water for normal filtration of ultrafiltration.

[0085] The above is only an illustration of the best embodiment of the present invention, but it should not be construed as a limitation of the claims. The present invention is not limited to the above embodiments, and its specific structure allows changes. Any changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.

[0086] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

Claims

1. An ozone-hydrogen peroxide coupled cleaning system for seawater desalination ultrafiltration membrane, characterized in that: It includes an ozone generation unit, an ozone and hydrogen peroxide dosing reaction unit, a pure gas washing branch unit, an ultrafiltration membrane unit and an exhaust gas treatment unit; The ozone generating unit is connected to the ozone and hydrogen peroxide adding reaction unit; The ozone and hydrogen peroxide dosing reaction unit comprises an ozone gas adding pipe (7), a hydrogen peroxide dosing pipe (8), a gas-liquid micro-nano dissolved gas pipe (9), and a liquid-liquid high-speed mixing pipe (10). The outlet of the ozone generating unit is divided into two routes, one route is connected to the gas-liquid micro-nano dissolved gas pipe (9) through the ozone gas adding pipe (7), the gas-liquid micro-nano dissolved gas pipe (9) and the hydrogen peroxide dosing pipe (8) are connected to the liquid-liquid high-speed mixing pipe (10), and the liquid-liquid high-speed mixing pipe (10) is connected to the ultrafiltration membrane unit; the other pure gas washing branch unit at the outlet of the ozone generating unit is connected to the ultrafiltration membrane unit; and the ultrafiltration membrane unit is connected to the tail gas disposal unit.

2. The ozone-hydrogen peroxide coupled cleaning system for seawater desalination ultrafiltration membrane according to claim 1, characterized in that: It also includes a concentrated water discharge pipe (18) arranged at the upper part of the ultrafiltration membrane unit and a backwash water discharge pipe (19) arranged at the bottom of the ultrafiltration membrane unit. The concentrated water discharge pipe (18) and the backwash water discharge pipe (19) are connected to the tail gas treatment unit.

3. The ozone-hydrogen peroxide coupled cleaning system for seawater desalination ultrafiltration membrane according to claim 1, characterized in that: The ozone generating unit comprises an air source ozone generator (2), an air compressor (3) and an ozone compression storage tank (4); the air source ozone generator (2) is connected to the air compressor (3), and the air compressor (3) is connected to the ozone compression storage tank (4).

4. The ozone-hydrogen peroxide coupled cleaning system for seawater desalination ultrafiltration membrane according to claim 1, characterized in that: The pure gas washing branch unit comprises a compressed ozone gas delivery pipe (13), a pressure reducing valve (14), a pressure tester (15), a gas washing controller (16) and a gas washing air inlet pipe (17). The compressed ozone gas delivery pipe (13) is connected to the ultrafiltration membrane unit via the pressure reducing valve (14), the pressure tester (15), the gas washing controller (16) and the gas washing air inlet pipe (17).

5. The ozone-hydrogen peroxide coupled cleaning system for seawater desalination ultrafiltration membrane according to claim 4, characterized in that: The ultrafiltration membrane unit comprises a raw water tank (1), an ultrafiltration water inlet pipe (6) and an ultrafiltration device (12); the raw water tank (1) is connected to the ultrafiltration water inlet pipe (6), the ultrafiltration water inlet pipe (6) is connected to the ultrafiltration device (12), a liquid-liquid high-speed mixing pipe (10) and an air washing air inlet pipe (17) are connected to the ultrafiltration device (12), an ultrafiltration water outlet pipe (22) is also arranged on the top of the ultrafiltration device (12), the ultrafiltration water outlet pipe (22) is connected to an ultrafiltration clear water pool (24), and the ultrafiltration clear water pool (24) is connected to a gas-liquid micro-nano dissolved gas pipe (9).

6. An ozone-hydrogen peroxide coupled cleaning method for seawater desalination ultrafiltration membrane based on the system of claim 5, characterized in that: The following steps are involved: 1) Ozone is fed into the air washing inlet pipe (17) through the compressed ozone gas delivery pipe (13) and the pressure reducing valve (14), and then enters the ultrafiltration device (12) for cleaning; 2) The water and ozone in the ultrafiltration clear water pool (24) are transported to the liquid-liquid high-speed mixing tube (10) through the gas-liquid micro-nano dissolved gas tube (9), and hydrogen peroxide is added to the liquid-liquid high-speed mixing tube (10). The gas-liquid mixture in the liquid-liquid high-speed mixing tube (10) enters the ultrafiltration device (12) for backwashing.

7. The ozone-hydrogen peroxide coupled cleaning method for seawater desalination ultrafiltration membrane according to claim 6, characterized in that: Ozone quantity Q O3 The following formula (1) is used for control: Q O3 =Q s ×[C0+K P ×(C t -C0)] (1) Q O3 ——Ozone dosage, g / h; Q s ——Backwash water flow, m 3 / h; C0——target ozone concentration, g / m 3 ; K p ——is the proportional adjustment coefficient; C t ——Ozone concentration measured by online ozone monitoring sensor.

8. The ozone-hydrogen peroxide coupled cleaning method for seawater desalination ultrafiltration membrane according to claim 7, characterized in that: The target ozone concentration is calculated by the following formula: k1——empirical coefficient; T1——adjust the pressure to a constant value, filter the water sample using a 0.45μm membrane, and the time required to initially collect 500mL of water sample, s; T2——The time required to collect 500mL of water sample again after continuous filtration for t minutes, s; t——the interval between two samplings, s.

9. The ozone-hydrogen peroxide coupled cleaning method for seawater desalination ultrafiltration membrane according to claim 6, characterized in that: In step 1), the time for entering the ultrafiltration device (12) for cleaning is 5 minutes, and the outlet pressure of the pressure reducing valve (14) is 0.1 MPa.

10. The ozone-hydrogen peroxide coupled cleaning method for seawater desalination ultrafiltration membrane according to claim 6, characterized in that: In step 2), the mass ratio of ozone and hydrogen peroxide is O3:H2O2=1:1-1:1.2, and the gas-liquid mixture in the liquid high-speed mixing tube (10) enters the ultrafiltration device (12) for backwashing for 20min-30min.

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