Membrane cleaning agent for removing microbial pollution as well as preparation method and application of membrane cleaning agent

Abstract

The invention belongs to the technical field of membrane cleaning agents, and particularly relates to a membrane cleaning agent for removing microbial pollution as well as a preparation method and application of the membrane cleaning agent. The membrane cleaning agent comprises the following components: a stripping agent, a non-oxidized bactericide, a biological enzyme, an enzyme stabilizer, a bactericidal synergist and water, the stripping agent is an epoxy alkyl compound; the enzyme stabilizer is glycerol and / or propylene glycol; the bactericidal synergist is trimethoprem and / or diamethoprem, and the bactericidal synergist is trimethoprem and / or diamethoprem. The cleaning agent is characterized in that the stripping agent, the non-oxidation type bactericide, the biological enzyme, the enzyme stabilizer and the sterilization synergist are used as main components, the cleaning effect is synergistically improved from the two aspects of enhancing the stripping and elution effect and the sterilization effect of the cleaning agent, and microbial contamination on a membrane is efficiently removed; the membrane flux is greatly improved compared with that before cleaning, and the desalting performance is basically the same as that before cleaning.

Description

Technical Field

[0001] This invention belongs to the field of membrane cleaning agent technology, specifically relating to a membrane cleaning agent for removing microbial contamination, its preparation method, and its application. Background Technology

[0002] With the widespread application of various membrane separation technologies (such as nanofiltration membranes, ultrafiltration membranes, and reverse osmosis membranes) and devices in water treatment fields such as advanced drinking water treatment and wastewater reuse, membrane fouling has gradually become a key bottleneck restricting its performance and economic benefits, attracting attention. Membrane fouling includes inorganic fouling, organic fouling, and microbial fouling. Compared with the other two types of fouling, microbial fouling is considered the most complex and difficult to control type of fouling due to its unique formation mechanism and difficulty in treatment, and cleaning is also extremely difficult. Microorganisms include algae, bacteria, fungi and their spores, tubers, and viruses. In the process of microbial fouling formation, large molecules such as organic matter (humus, polysaccharides) in the influent are first adsorbed onto the membrane surface, becoming conditions for microbial survival. Subsequently, microorganisms rapidly multiply on the membrane, forming microbial fouling. The biological slime formed by microbial fouling is insoluble in acids and sparingly soluble in alkalis, and is almost unaffected by water flow shear force, making it difficult to wash away even with repeated flushing. After the formation of microbial fouling, it will significantly reduce water production, rapidly increase operating pressure, increase energy consumption, and affect normal on-site production.

[0003] Currently, the commonly used cleaning methods in the industry involve using strong acid or strong alkali solutions. Strong acid solutions are effective at treating inorganic contaminants, but less effective at treating organic or microbial contaminants. High concentrations of strong alkali solutions are generally required to remove microbial contaminants, but these high concentrations can significantly damage the membrane structure, reducing its filtration performance. Another method involves adding oxidizing disinfectants or bactericides for membrane cleaning, but this carries the risk of oxidative damage to the membrane. Furthermore, bactericides primarily target suspended microorganisms and have poor penetration into established, mature biofilms, resulting in limited cleaning effectiveness. In recent years, enzyme-catalyzed cleaning technology has gradually become a research hotspot. Enzymes, as biocatalysts, possess significant advantages such as high efficiency, specificity, and mildness. They can specifically hydrolyze key components in biofilms, thereby achieving effective biofilm disintegration and removal. For example, patent document CN105169953A reports an enzyme cleaning agent for cleaning microbial contamination of reverse osmosis membranes. It mainly removes microbial contamination through the action of biological enzymes. However, the cleaning effect achieved by biological enzymes alone is poor. Furthermore, the enzyme stabilizer in its formula is sucrose. In fact, sucrose can also serve as a carbon source necessary for the survival and reproduction of microorganisms, which may further aggravate microbial contamination.

[0004] Therefore, it is necessary to develop a membrane cleaning agent that can safely and efficiently remove microbial contamination, reduce damage to the membrane structure during the cleaning process, and ensure that the membrane retains its high desalination performance after cleaning. Summary of the Invention

[0005] One of the objectives of this invention is to address the problem of poor cleaning effect of existing membrane cleaning agents by providing a safe and efficient membrane cleaning agent that can effectively remove microbial contamination on the membrane, significantly increase membrane flux, and ensure that the cleaned membrane continues to maintain high desalination performance.

[0006] Specifically, the membrane cleaning agent contains the following components: a stripping agent, a non-oxidizing bactericide, a biological enzyme, an enzyme stabilizer, a bactericidal synergist, and water; the stripping agent is an epoxy alkyl compound; the enzyme stabilizer is glycerol and / or propylene glycol; and the bactericidal synergist is trimethoprim and / or dimethoprim.

[0007] In a preferred embodiment, based on a total mass of 100.0 wt% of the membrane cleaning agent, the content of the stripping agent is 2.0~4.0 wt%, the content of the non-oxidizing bactericide is 3.0~6.0 wt%, the content of the biological enzyme is 2.0~5.0 wt%, the content of the enzyme stabilizer is 0.5~1.5 wt%, the content of the bactericidal synergist is 1.0~3.0 wt%, and the remainder is water.

[0008] In a preferred embodiment, the stripping agent is selected from at least one of 1,2-epoxybutane, 2,3-epoxybutane, 1,2-epoxypentane, 2,3-epoxypentane, 1,2-epoxyhexane, and 1,2-epoxyheptane.

[0009] In a preferred embodiment, the non-oxidizing bactericide is selected from at least one of isothiazolinone, dithiocyanomethane, benzalkonium bromide, and benzalkonium chloride.

[0010] In a preferred embodiment, the bioenzyme is selected from at least one of lysozyme, pectinase, lipase, protease, glucanase, chitinase, amylase, and cellulase.

[0011] In a preferred embodiment, the bio-enzyme is a complex enzyme comprising lysozyme, pectinase, lipase, and protease, wherein the mass ratio of lysozyme, pectinase, lipase, and protease is 1:(1~3):(1~3):(0.5~2).

[0012] A second objective of this invention is to provide a method for preparing the aforementioned membrane cleaning agent for removing microbial contamination. The preparation method is as follows: A stripping agent, a non-oxidizing bactericide, a biological enzyme, an enzyme stabilizer, and a bactericidal synergist are mixed and dissolved with water; the resulting mixture is the membrane cleaning agent.

[0013] In a preferred embodiment, the mixing process of each raw material component in the preparation method is as follows: first, the stripping agent, enzyme stabilizer, bactericidal synergist and water are stirred until completely dissolved, and then a non-oxidizing bactericide and biological enzyme are added for a second stirring treatment. The resulting mixture is the membrane cleaning agent.

[0014] In a preferred embodiment, the first stirring treatment is performed at a speed of 60-80 r / min for a time of 0.5-1.5 h.

[0015] In a preferred embodiment, the second stirring treatment is performed at a speed of 20-40 r / min for a time of 1.0-3.0 h.

[0016] A third objective of this invention is to provide the application of the above-mentioned membrane cleaning agent for removing microbial contamination in the membrane cleaning process.

[0017] In a preferred embodiment, the membrane cleaning method includes the following steps: the membrane cleaning agent is prepared into a working solution and then delivered to a container holding the membrane to be cleaned; in the first stage, the membrane is circulated and cleaned at a low flow rate; in the second stage, the membrane is circulated and cleaned at a high flow rate; in the third stage, the membrane is immersed and circulated at a low flow rate at 30~50°C; after the working solution is discharged, the membrane is rinsed with clean water.

[0018] In a preferred embodiment, the concentration of the membrane cleaning agent in the working fluid is 1-10%.

[0019] In a preferred embodiment, the operating pressure of the first stage is 5-7 bar, the membrane surface flow rate is 0.8-1.2 m / s, and the time is 5-15 min.

[0020] In a preferred embodiment, the operating pressure of the second stage is 8-12 bar, the membrane surface flow rate is 1.8-2.2 m / s, and the time is 30-50 min.

[0021] In a preferred embodiment, the operating pressure of the third stage is 5-7 bar, the membrane surface flow rate is 0.8-1.2 m / s, and the time is 2.0-4.0 h.

[0022] Beneficial effects: The key to this invention lies in using a stripping agent, a non-oxidizing bactericide, a biological enzyme, an enzyme stabilizer, and a bactericidal synergist as the main components. The cleaning agent obtained by this compound has a synergistic effect of sterilization and stripping biological slime, which can efficiently remove microbial contamination on the membrane, resulting in a significant increase in membrane flux compared to before cleaning, while the desalination performance is basically the same as before cleaning. Among them, epoxy alkyl compounds are used as stripping agents, which can penetrate into the microbial slime on the membrane and undergo ring-opening reactions under cleaning conditions, further enhancing hydrophilicity and wettability. By reducing the interfacial adhesion energy between the membrane surface and pollutants, penetrating the loose fouling layer, and inhibiting pollutant redeposition, efficient stripping of organic colloids, biological slime, and mud cake is achieved. Compared with oxidizing disinfectants, non-oxidizing bactericides kill microorganisms by acting on specific sites of microorganisms with toxicity. The addition of non-oxidizing bactericides will not damage the membrane structure. At the same time, the added trimethoprim or dimethoprim bactericidal synergists work synergistically with the non-oxidizing bactericides to further improve the bactericidal effect of the membrane cleaning agent. Bioenzymes have a mild catalytic bactericidal effect, and glycerol or propylene glycol are used as enzyme stabilizers, which can ensure the activity of bioenzymes and avoid providing carbon source conditions for microbial reproduction and agglomeration of microbial contamination. In summary, the membrane cleaning agent provided by this invention synergistically improves the cleaning effect by enhancing both the stripping and elution effect and the bactericidal effect of the cleaning agent, ensuring that the cleaned membrane has both high membrane flux performance and desalination rate. Moreover, the raw materials used in this membrane cleaning agent are low in toxicity, simple to prepare, safe and efficient. Detailed Implementation

[0023] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Furthermore, unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present invention.

[0024] The membrane cleaning agent for removing microbial contamination provided by the present invention contains the following components: a stripping agent, a non-oxidizing bactericide, a biological enzyme, an enzyme stabilizer, a bactericidal synergist, and water; wherein the stripping agent is an epoxy alkyl compound; the enzyme stabilizer is glycerol and / or propylene glycol; and the bactericidal synergist is trimethoprim and / or dimethoprim.

[0025] In this invention, taking the total mass of the membrane cleaning agent as 100.0 wt%, the content of the stripping agent is preferably 2.0~4.0 wt%, such as 2.0 wt%, 2.5 wt%, 3.0 wt%, 3.5 wt%, 4.0 wt%, or any value between them; the content of the non-oxidizing bactericide is preferably 3.0~6.0 wt%, such as 3.0 wt%, 4.0 wt%, 5.0 wt%, 6.0 wt%, or any value between them; the content of the biological enzyme is preferably 2.0~5.0 wt%. The preferred concentrations of the raw materials in the membrane cleaning agent are 2.0 wt%, 3.0 wt%, 4.0 wt%, 5.0 wt%, or any value between them; the preferred concentrations of the enzyme stabilizer are 0.5-1.5 wt%, such as 0.5 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.5 wt%, or any value between them; the preferred concentrations of the bactericidal synergist are 1.0-3.0 wt%, such as 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, or any value between them; the remainder is water. Controlling the content of each raw material component in the membrane cleaning agent within the above-mentioned preferred ranges is more conducive to achieving a synergistic effect and improving the cleaning effect on the membrane.

[0026] In this invention, the stripping agent is an epoxy alkyl compound formed by an epoxy group and an alkyl group of a certain chain length. Its general chemical formula can be represented as R-HC(O)CH2 or R1-HC(O)CH-R2, wherein the R group is a C2-C5 alkyl group, and the R1 and R2 groups are each independently a C1-C3 alkyl group. Specific examples of C1-C5 alkyl groups include, but are not limited to: -CH2CH3, -CH2CH2CH3, -CH(CH3)2, -CH2CH2CH2CH3, -CH2CH2CH2CH2CH3, etc. Specific examples of C1-C3 alkyl groups include, but are not limited to: -CH3, -CH2CH3, -CH2CH2CH3, -CH(CH3)2, etc. The stripping agent is preferably an epoxy alkyl compound with a boiling point ≥50℃, which helps to broaden the applicable operating temperature window of the cleaning agent and avoids the reduction in cleaning effect due to the volatilization of low-boiling-point epoxy alkyl compounds caused by increased cleaning process temperature. Specific examples of the stripping agent include, but are not limited to, at least one of 1,2-epoxybutane, 2,3-epoxybutane, 1,2-epoxypentane, 2,3-epoxypentane, 1,2-epoxyhexane, and 1,2-epoxyheptane.

[0027] In this invention, non-oxidizing bactericides are chemical preparations that achieve bactericidal effects by destroying the structure of microbial cells or inhibiting their metabolic processes through adsorption, penetration, or interference with the activity of biological enzymes. Specific examples include, but are not limited to, at least one of isothiazolinone, dithiocyanomethane, benzalkonium bromide, and benzalkonium chloride.

[0028] In this invention, the bio-enzyme can be any one or more of the commonly used bio-enzymes in existing membrane cleaning agents, and specific examples include, but are not limited to, any one or more of lysozyme, pectinase, lipase, protease, glucanase, chitinase, amylase, and cellulase.

[0029] In one specific embodiment, the bio-enzyme is preferably a complex enzyme, including lysozyme, pectinase, lipase, and protease. The complex enzyme helps to better exert its catalytic bactericidal effect and further improves the cleaning effect. The preferred mass ratio of the lysozyme, pectinase, lipase, and protease is 1:(1~3):(1~3):(0.5~2). When the amount of lysozyme is 1 part by weight, the amount of pectinase is preferably 1~3 parts by weight, such as 1, 2, 3 parts by weight or any value between them; the amount of lipase is preferably 1~3 parts by weight, such as 1, 2, 3 parts by weight or any value between them; the amount of protease is preferably 0.5~2 parts by weight, such as 0.5, 1, 1.5, 2 parts by weight or any value between them.

[0030] The preparation method of the membrane cleaning agent for removing microbial contamination provided by the present invention is as follows: after mixing and dissolving the stripping agent, non-oxidizing bactericide, biological enzyme, enzyme stabilizer, bactericidal synergist and water, the resulting mixture is the membrane cleaning agent.

[0031] In this invention, the mixing order of the raw material components and water in the preparation method can be simultaneous or in a specific order. The preferred mixing process of the raw material components and water in the preparation method is as follows: first, the stripping agent, enzyme stabilizer, bactericidal synergist, and water are subjected to a first stirring treatment until completely dissolved; then, a non-oxidizing bactericide and a biological enzyme are added for a second stirring treatment. The resulting mixture is the membrane cleaning agent. Using the specific mixing order described above is more conducive to confirming the activity of the biological enzyme and the uniformity of the mixing of each raw material component during the mixing process. The preferred stirring speed for the first stirring treatment is 60~80 r / min, such as 60 r / min, 65 r / min, 70 r / min, 75 r / min, 80 r / min, or any value between them; the preferred time is 0.5~1.5 h, such as 0.5 h, 0.8 h, 1.0 h, 1.2 h, 1.5 h, or any value between them. The preferred stirring speed for the second stirring treatment is 20~40 r / min, such as 20 r / min, 25 r / min, 30 r / min, 35 r / min, 40 r / min or any value between them; the preferred time is 1.0~3.0 h, such as 1.0 h, 1.5 h, 2.0 h, 2.5 h, 3.0 h or any value between them.

[0032] This invention provides the application of the above-mentioned membrane cleaning agent for removing microbial contamination in the membrane cleaning process. It should be noted that the membrane cleaning agent provided by this invention is suitable for cleaning various types of membranes, such as ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes, and is also applicable to cleaning various types of membranes, such as flat sheet membranes, spiral wound membranes, and fiber membranes.

[0033] The membrane cleaning agent provided by this invention is applicable to various existing membrane cleaning procedures. A preferred membrane cleaning method includes the following steps: after preparing the membrane cleaning agent into a working solution, it is delivered to a container holding the membrane to be cleaned; in the first stage, the membrane is circulated and cleaned at a low flow rate; in the second stage, it is circulated and cleaned at a high flow rate; and in the third stage, it is immersed and circulated at a low flow rate at 30-50°C. After draining the working solution, the membrane is rinsed with clean water. The cleaning temperature in the third stage can be 30°C, 35°C, 40°C, 45°C, 50°C, or any value between them. The first stage involves low-flow-rate circulating cleaning to ensure the cleaning agent is evenly distributed across the membrane surface, allowing it to slowly penetrate the microbial biofilm fouling layer and establish a preliminary reaction interface for subsequent deep cleaning. The second stage involves high-flow-rate circulating cleaning. This utilizes hydraulic shear to enhance the removal of the microbial fouling layer and increases the collision frequency between enzymes, non-oxidizing bactericides, and the fouling layer, thus improving the bactericidal effect. Furthermore, the fluid shear heat effect gradually raises the system temperature, enhancing the catalytic bactericidal effect of the enzymes. The third stage involves low-flow-rate immersion cleaning at 30-50°C. This temperature ensures high enzyme activity without damaging the membrane, allowing the stripping agent, non-oxidizing bactericide, and enzymes to further penetrate the microbial biofilm fouling layer for deep cleaning. In other words, this specific three-stage cleaning method achieves better cleaning results.

[0034] In this invention, the concentration of the membrane cleaning agent in the working fluid can be any conventional choice in the art, preferably 1 to 10%, such as 1%, 2%, 5%, 8%, 10% or any value between them.

[0035] In this invention, the operating pressure of the first stage is preferably 5 to 7 bar, such as 5 bar, 5.5 bar, 6 bar, 6.5 bar, 7 bar or any value between them; the membrane surface flow rate is preferably 0.8 to 1.2 m / s, such as 0.8 m / s, 0.9 m / s, 1.0 m / s, 1.1 m / s, 1.5 m / s or any value between them; and the time is preferably 5 to 15 min, such as 5 min, 8 min, 10 min, 12 min, 15 min or any value between them.

[0036] In this invention, the operating pressure of the second stage is preferably 8 to 12 bar, such as 8 bar, 9 bar, 10 bar, 11 bar, 12 bar or any value between them; the membrane surface flow rate is preferably 1.8 to 2.2 m / s, such as 1.8 m / s, 1.9 m / s, 2.0 m / s, 2.1 m / s, 2.2 m / s or any value between them; and the time is preferably 30 to 50 min, such as 30 min, 35 min, 40 min, 45 min, 50 min or any value between them.

[0037] In this invention, the operating pressure of the third stage is preferably 5 to 7 bar, such as 5 bar, 5.5 bar, 6 bar, 6.5 bar, 7 bar or any value between them; the membrane surface flow rate is preferably 0.8 to 1.2 m / s, such as 0.8 m / s, 0.9 m / s, 1.0 m / s, 1.1 m / s, 1.5 m / s or any value between them; the time is preferably 2.0 to 4.0 h, such as 2.0 h, 2.5 h, 3.0 h, 3.5 h, 4.0 h or any value between them.

[0038] The present invention will be described in detail below through specific embodiments. These embodiments are intended to explain the invention and should not be construed as limiting it. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0039] In the following examples and comparative examples, the microbially contaminated membrane sheets to be cleaned came from a DTRO membrane column used at a landfill leachate treatment site, where microbial contamination was severe and stable operation was impossible.

[0040] Example 1 This embodiment illustrates the preparation of a membrane cleaning agent and a membrane cleaning method, as detailed below: (1) Preparation of membrane cleaning agent: Add 89.0 wt% water to a container according to the ratio, turn on the stirring device, then add 2.0 wt% 1,2-epoxypentane, 0.5 wt% glycerol and 2.0 wt% trimethoprim, stir at 60 r / min for 1 h until all components are completely dissolved, then add 3.0 wt% isothiazolinone and 3.0 wt% biological enzyme (mass ratio of lysozyme: pectinase: lipase: protease = 1:2:2:1), stir at 30 r / min for 2 h to obtain a uniform mixture, which is the membrane cleaning agent.

[0041] (2) Membrane cleaning method: Water washing: Turn on the feed pump and the high-pressure pump, and circulate tap water at a high flow rate (membrane surface flow rate of about 3.0 m / s) for about 10 minutes, with an operating pressure of 20 bar; Membrane cleaning agent cleaning: The membrane cleaning agent obtained in step (1) is first prepared into a working solution with a concentration of 5% by water. In the first stage, the feed pump is turned on, the working solution is pumped in at a low flow rate, the operating pressure is 6 bar, the membrane surface flow rate is 1.0 m / s, and the cleaning is circulated for 10 min. In the second stage, the high pressure pump is turned on, and the cleaning is circulated at a high flow rate until the raw water temperature rises to 40℃, the operating pressure is 10 bar, the membrane surface flow rate is about 2.0 m / s, and the time is about 40 min. In the third stage, the high pressure pump is turned off, and the membrane is soaked and circulated at a low flow rate at 40±1℃ for 3 h, the operating pressure is 6 bar, and the membrane surface flow rate is about 1.0 m / s. Washing: Rinse with tap water, drain the concentrated water, and stop rinsing when the pH of the concentrated water is neutral.

[0042] Example 2 This embodiment illustrates the preparation of a membrane cleaning agent and a membrane cleaning method, as detailed below: (1) Preparation of membrane cleaning agent: Add 88.0 wt% water to a container according to the ratio, turn on the stirring device, then add 3.0 wt% 1,2-epoxybutane, 1.0 wt% glycerol and 3.0 wt% trimethoprim, stir at 60 r / min for 1 h until all components are completely dissolved, then add 4.0 wt% benzalkonium bromide and 2.0 wt% biological enzyme (mass ratio of lysozyme: pectinase: lipase: protease = 1:2:2:2), stir at 30 r / min for 2 h to obtain a uniform mixture, which is the membrane cleaning agent.

[0043] (2) Membrane cleaning method: Membrane cleaning is performed according to the method described in step (2) of Example 1.

[0044] Example 3 This embodiment illustrates the preparation of a membrane cleaning agent and a membrane cleaning method, as detailed below: (1) Preparation of membrane cleaning agent: Add 85.0 wt% water to a container according to the ratio, turn on the stirring device, then add 4.0 wt% 1,2-epoxyhexane, 1.5 wt% glycerol and 2.0 wt% dimethoprim, stir at 60 r / min for 1 h until all components are completely dissolved, then add 4.0 wt% dioxocyanomethane and 5.0 wt% biological enzyme (mass ratio of lysozyme: pectinase: lipase: protease = 1:1:3:1), stir at 30 r / min for 2 h to obtain a uniform mixture, which is the membrane cleaning agent.

[0045] (2) Membrane cleaning method: Membrane cleaning is performed according to the method described in step (2) of Example 1.

[0046] Example 4 This embodiment illustrates the preparation of a membrane cleaning agent and a membrane cleaning method, as detailed below: (1) Preparation of membrane cleaning agent: Add 84.0 wt% water to a container according to the ratio, turn on the stirring device, then add 4.0 wt% 2,3-epoxybutane, 1.0 wt% glycerol and 3.0 wt% dimethoprim, stir at 60 r / min for 1 h until all components are completely dissolved, then add 5.0 wt% dioxocyanomethane and 3.0 wt% biological enzyme (mass ratio of lysozyme: pectinase: lipase: protease = 1:2:2:1), stir at 30 r / min for 2 h to obtain a uniform mixture, which is the membrane cleaning agent.

[0047] (2) Membrane cleaning method: Water washing: Turn on the feed pump and the high-pressure pump, and circulate tap water at a high flow rate (membrane surface flow rate of about 3.0 m / s) for about 10 minutes, with an operating pressure of 20 bar; Membrane cleaning agent cleaning: The membrane cleaning agent obtained in step (1) is first prepared into a working solution with a concentration of 2% by water. In the first stage, the feed pump is turned on, the working solution is pumped in at a low flow rate, the operating pressure is 5 bar, the membrane surface flow rate is 0.8 m / s, and the cleaning is circulated for 15 min. In the second stage, the high pressure pump is turned on, and the cleaning is circulated at a high flow rate until the raw water temperature rises to 50℃, the operating pressure is 12 bar, the membrane surface flow rate is about 2.2 m / s, and the time is about 50 min. In the third stage, the high pressure pump is turned off, and the membrane is soaked and circulated at a low flow rate at 50±1℃ for 2 h, the operating pressure is 5 bar, and the membrane surface flow rate is about 0.8 m / s. Washing: Rinse with tap water, drain the concentrated water, and stop rinsing when the pH of the concentrated water is neutral.

[0048] Example 5 This embodiment illustrates the preparation of a membrane cleaning agent and a membrane cleaning method, as detailed below: (1) Preparation of membrane cleaning agent: Add 83.0 wt% water to a container according to the ratio, turn on the stirring device, then add 4.0 wt% 2,3-epoxybutane, 1.0 wt% glycerol and 2.0 wt% trimethoprim, stir at 60 r / min for 1 h until all components are completely dissolved, then add 6.0 wt% isothiazolinone and 4.0 wt% biological enzyme (mass ratio of lysozyme: pectinase: lipase: protease = 1:3:1:1), stir at 30 r / min for 2 h to obtain a uniform mixture, which is the membrane cleaning agent.

[0049] (2) Membrane cleaning method: Membrane cleaning is performed according to the method described in step (2) of Example 1.

[0050] Water washing: Turn on the feed pump and the high-pressure pump, and circulate tap water at a high flow rate (membrane surface flow rate of about 3.0 m / s) for about 10 minutes, with an operating pressure of 20 bar; Membrane cleaning agent cleaning: The membrane cleaning agent obtained in step (1) is first prepared into a working solution with a concentration of 8% by water. In the first stage, the feed pump is turned on, the working solution is pumped in at a low flow rate, the operating pressure is 7 bar, the membrane surface flow rate is 1.2 m / s, and the cleaning is circulated for 5 min. In the second stage, the high pressure pump is turned on, and the cleaning is circulated at a high flow rate until the raw water temperature rises to 30℃, the operating pressure is 8 bar, the membrane surface flow rate is about 1.8 m / s, and the time is about 30 min. In the third stage, the high pressure pump is turned off, and the membrane is soaked and circulated at a low flow rate at 30±1℃ for 4 h, the operating pressure is 7 bar, and the membrane surface flow rate is about 1.2 m / s. Washing: Rinse with tap water, drain the concentrated water, and stop rinsing when the pH of the concentrated water is neutral.

[0051] Comparative Example 1 (1) Acidic cleaning agent: Xiamen Jiarong Technology Co., Ltd., model A1301L.

[0052] (2) Membrane cleaning method: Membrane cleaning is performed according to the method described in step (2) of Example 1.

[0053] Comparative Example 2 (1) Alkaline cleaning agent: Xiamen Jiarong Technology Co., Ltd., model C1303L.

[0054] (2) Membrane cleaning method: Membrane cleaning is performed according to the method described in step (2) of Example 1.

[0055] Comparative Example 3 (1) Commercially available microbial contamination cleaning agent: purchased from Qualcomm Chemicals, USA, product number GCT-K300.

[0056] (2) Membrane cleaning method: Membrane cleaning is performed according to the method described in step (2) of Example 1.

[0057] Comparative Example 4 This comparative example illustrates the preparation of a reference membrane cleaning agent and a membrane cleaning method, as detailed below: (1) Preparation of reference membrane cleaning agent: The reference membrane cleaning agent was prepared according to the method in (1) of Example 1, except that the amount of 1,2-epoxypentane added was 0, and the other conditions were the same as those in (1) of Example 1.

[0058] (2) Membrane cleaning method: Membrane cleaning is performed according to the method described in step (2) of Example 1.

[0059] Comparative Example 5 This comparative example illustrates the preparation of a reference membrane cleaning agent and a membrane cleaning method, as detailed below: (1) Preparation of reference membrane cleaning agent: The reference membrane cleaning agent was prepared according to the method in (1) of Example 1, except that the amount of trimethoprim added was 0, and the other conditions were the same as those in (1) of Example 1.

[0060] (2) Membrane cleaning method: Membrane cleaning is performed according to the method described in step (2) of Example 1.

[0061] Comparative Example 6 This comparative example illustrates the preparation of a reference membrane cleaning agent and a membrane cleaning method, as detailed below: (1) Preparation of reference membrane cleaning agent: The reference membrane cleaning agent was prepared according to the method in (1) of Example 1, except that the amount of isothiazolinone added was 0, and the other conditions were the same as those in (1) of Example 1.

[0062] (2) Membrane cleaning method: Membrane cleaning is performed according to the method described in step (2) of Example 1.

[0063] Test case The membrane flux and desalination rate of the membrane before and after cleaning were tested using the following method, and the results are shown in Table 1.

[0064] (1) Sterilization effect test: Take 100 mL of landfill leachate into a 250 mL Erlenmeyer flask, then add 10 mL of cleaning agent (membrane cleaning agent from each example and comparative example), and incubate overnight in a shaker at 37 °C; take 100 μL from the overnight incubated solution and spread it in a 9 cm petri dish (prepared LB solid culture base in the petri dish), and incubate overnight in a shaker at 37 °C; set up a blank sample (follow the same steps as above, but without adding cleaning agent), then take out the petri dish incubated overnight, count the colonies, and calculate the sterilization rate. The results are shown in Table 1.

[0065] Table 1

[0066] As shown in Table 1, compared with the comparative examples, especially conventional acidic cleaning agents, alkaline cleaning agents and commercially available microbial contamination cleaning agents, the membrane cleaning agent provided in this embodiment of the invention has a significantly improved bactericidal effect.

[0067] (2) Membrane flux test: Pure water was used for the test at 55 bar. The results are shown in Table 2.

[0068] (3) Membrane desalination rate test: The test was conducted using a 32000 mg / L NaCl solution at 55 bar. The results are shown in Table 2.

[0069] Table 2

[0070] As shown in Table 2, compared with the membrane cleaning agent provided in the comparative example, the membrane cleaning agent provided in this embodiment of the invention exhibits a superior cleaning effect, with a greater increase in membrane flux after cleaning, while maintaining a high level of membrane desalination performance. Furthermore, a comparison between Comparative Example 4 and Example 1 shows that when the amount of 1,2-epoxypentane added is 0, the bactericidal effect of Comparative Example 4 is actually higher than that of Example 1, but the increase in clean water flux after cleaning is significantly less than that of Example 1. This indicates that the bactericidal effect is not the only factor affecting the cleaning effect of the membrane cleaning agent, and also indirectly verifies that the combination of stripping agent, non-oxidizing bactericide, biological enzyme, enzyme stabilizer, and bactericidal synergist in the membrane cleaning agent provided by this invention produces a synergistic effect of bactericidal action and removal of biological slime, thereby achieving a significant increase in membrane flux.

[0071] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A membrane cleaning agent for removing microbial contamination, characterized in that, The membrane cleaning agent contains the following components: a stripping agent, a non-oxidizing bactericide, a biological enzyme, an enzyme stabilizer, a bactericidal synergist, and water; the stripping agent is an epoxy alkyl compound; the enzyme stabilizer is glycerol and / or propylene glycol; and the bactericidal synergist is trimethoprim and / or dimethoprim.

2. The membrane cleaning agent for removing microbial contamination according to claim 1, characterized in that, Based on a total mass of 100.0 wt% for the membrane cleaning agent, the content of the stripping agent is 2.0~4.0 wt%, the content of the non-oxidizing bactericide is 3.0~6.0 wt%, the content of the biological enzyme is 2.0~5.0 wt%, the content of the enzyme stabilizer is 0.5~1.5 wt%, the content of the bactericidal synergist is 1.0~3.0 wt%, and the remainder is water.

3. The membrane cleaning agent for removing microbial contamination according to claim 1, characterized in that, The stripping agent is selected from at least one of 1,2-epoxybutane, 2,3-epoxybutane, 1,2-epoxypentane, 2,3-epoxypentane, 1,2-epoxyhexane, and 1,2-epoxyheptane.

4. The membrane cleaning agent for removing microbial contamination according to claim 1, characterized in that, The non-oxidizing bactericide is selected from at least one of isothiazolinone, dithiocyanomethane, benzalkonium bromide, and benzalkonium chloride.

5. The membrane cleaning agent for removing microbial contamination according to claim 1, characterized in that, The bioenzyme is selected from at least one of lysozyme, pectinase, lipase, protease, glucanase, chitinase, amylase, and cellulase.

6. The membrane cleaning agent for removing microbial contamination according to claim 5, characterized in that, The bio-enzyme is a complex enzyme including lysozyme, pectinase, lipase and protease, wherein the mass ratio of lysozyme, pectinase, lipase and protease is 1:(1~3):(1~3):(0.5~2).

7. The method for preparing the membrane cleaning agent for removing microbial contamination according to any one of claims 1 to 6, characterized in that, The preparation method is as follows: after mixing and dissolving the stripping agent, non-oxidizing bactericide, biological enzyme, enzyme stabilizer, bactericidal synergist and water, the resulting mixture is the membrane cleaning agent.

8. The method for preparing the membrane cleaning agent for removing microbial contamination according to claim 7, characterized in that, The mixing process of each raw material component in the preparation method is as follows: First, the stripping agent, enzyme stabilizer, bactericidal synergist and water are stirred until completely dissolved. Then, a non-oxidizing bactericide and biological enzyme are added and stirred for a second time. The resulting mixture is the membrane cleaning agent. Preferably, the stirring speed of the first stirring treatment is 60~80 r / min, and the time is 0.5~1.5 h; Preferably, the second stirring treatment is performed at a speed of 20-40 r / min for a time of 1.0-3.0 h.

9. The application of the membrane cleaning agent for removing microbial contamination as described in any one of claims 1 to 8 in the membrane cleaning process.

10. The application of the membrane cleaning agent for removing microbial contamination according to claim 9 in the membrane cleaning process, characterized in that, The membrane cleaning method includes the following steps: the membrane cleaning agent according to any one of claims 1 to 8 is prepared into a working solution and then delivered to a container holding the membrane to be cleaned. In the first stage, the membrane is circulated and cleaned at a low flow rate. In the second stage, the membrane is circulated and cleaned at a high flow rate. In the third stage, the membrane is immersed and circulated at a low flow rate at 30 to 50°C. After the working solution is discharged, the membrane is rinsed with clean water. Preferably, the concentration of the membrane cleaning agent in the working fluid is 1-10%; Preferably, the operating pressure in the first stage is 5~7 bar, the membrane surface flow rate is 0.8~1.2 m / s, and the time is 5~15 min; Preferably, the operating pressure in the second stage is 8~12 bar, the membrane surface flow rate is 1.8~2.2 m / s, and the time is 30~50 min; Preferably, the operating pressure of the third stage is 5~7 bar, the membrane surface flow rate is 0.8~1.2 m / s, and the time is 2.0~4.0 h.

Images