A reverse osmosis membrane cleaning agent composed of a non-oxidizing bactericide and an enzyme and its application.

Abstract

This invention relates to the field of water treatment technology, specifically to a reverse osmosis membrane cleaning agent composed of a non-oxidizing bactericide and an enzyme, and its application. Its main purpose is to remove biofouling from reverse osmosis membranes and restore membrane flux. This patent discloses a novel reverse osmosis membrane cleaning agent formulation. Considering the different pH requirements of the cleaning agent in actual production, different types of bioactive hydrolytic enzymes are selected to disrupt the structure of bacterial cell walls and their extracellular polymers. A reducing agent and a non-oxidizing bactericide are combined to enhance the cleaning effect of the reverse osmosis membrane. For different cleaning purposes, non-oxidizing bactericides suitable for acidic and alkaline cleaning are formulated. Sodium benzoate and benzalkonium chloride show good application prospects in the removal of reverse osmosis membrane fouling.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a reverse osmosis membrane cleaning agent composed of a non-oxidizing bactericide and an enzyme, and its application. Its main purpose is to remove biofouling from reverse osmosis membranes and restore membrane flux. Background Technology

[0002] The fouling of reverse osmosis membranes during application determines their lifespan. Based on the different types of contaminants they remove, reverse osmosis membrane fouling can be categorized into inorganic salt fouling, organic salt fouling, and biofouling. Biofouling occurs when bacteria remaining on the reverse osmosis membrane secrete metabolic products such as proteins, polysaccharides, and eDNA, forming a dense and sticky biofilm that clogs the membrane pores and reduces membrane flux. Furthermore, since the commonly used reverse osmosis membrane structure on the market is a spiral winding type, it is not easy to clean. Once biological contaminants accumulate and form a biofilm structure, it is difficult to remove them subsequently.

[0003] In reverse osmosis membrane fouling control projects, alternating acid-base cleaning methods are commonly used. Under acidic and alkaline conditions, cleaning agents focus on different aspects of removing reverse osmosis membrane fouling. Acid washing removes most inorganic fouling, while alkaline washing is beneficial for removing biological fouling. Most reverse osmosis membrane fouling types involve a coexistence of inorganic and biological fouling. Therefore, alternating acid-base cleaning is a relatively effective cleaning method. However, facing the most difficult-to-remove biological fouling, bacteria accumulate on the reverse osmosis membrane surface, secreting biological organic matter containing proteins, polysaccharides, and extracellular DNA, forming a robust biofilm system. Conventional acid-base cleaning agents alone are insufficient. Therefore, it is necessary to improve the acid-base formulation to better address stubborn biological fouling while simultaneously removing inorganic fouling. Bioactive hydrolases, as highly efficient catalytic cleaning agents, require only small amounts and have strong specificity. They can effectively disrupt the structure of cell walls and extracellular polymers. Adding bioactive hydrolases to acid-base cleaning formulations is beneficial for removing extracellular polymers.

[0004] Based on the above background, this patent invention provides a novel reverse osmosis membrane cleaning agent formulation. According to the different pH values ​​of the cleaning agent, corresponding non-oxidizing bactericides, reducing agents, and bioactive hydrolytic enzymes are selected. In practical applications, acid-base alternating cleaning or using one of the formulations alone can be adopted to disintegrate the biofilm system formed on the reverse osmosis membrane and improve cleaning efficiency. Summary of the Invention

[0005] Based on the problems raised in the background art, this patent invention provides a novel reverse osmosis membrane cleaning agent formulation. Considering the different requirements for the pH value of the cleaning agent in actual production, different types of bioactive hydrolytic enzymes are selected to destroy the structure of bacterial cell walls and their extracellular polymers, and combined with reducing agents and non-oxidizing bactericides to enhance the cleaning effect of reverse osmosis membranes.

[0006] This invention provides a reverse osmosis membrane cleaning agent, achieved through the following technical solution:

[0007] An improved acid-base cleaning agent formulation includes both acidic and alkaline cleaning agents; depending on the degree of reverse osmosis membrane fouling, alternating acid-base cleaning or choosing one of them may be necessary.

[0008] Based on 100% of the total mass of the cleaning agent, the acidic cleaning agent includes the following components: 1%-10% metal chelating agent, 1%-10% reducing agent, 0.5%-10% bioactive hydrolytic enzyme, and 1%-10% non-oxidizing bactericide.

[0009] Based on 100% of the total mass of the cleaning agent, the alkaline cleaning agent includes the following components: 1%-10% metal chelating agent, 1%-10% reducing agent, 0.5%-10% mixed bioactive hydrolytic enzyme, and 1%-10% non-oxidizing bactericide.

[0010] Preferably, in the formulations of acidic and alkaline cleaning agents, the metal chelating agent is selected as tetrasodium ethylenediaminetetraacetate (EDTA). The preferred chelating agent of this invention is tetrasodium EDTA, as the hydrolysis products and colloidal particle morphology of tetrasodium EDTA have a strong influence, readily complexing the cations in the deposited sulfate scale, thereby enabling the deposits to gradually transfer into the solution and playing a stripping role during the cleaning process.

[0011] Preferably, sodium bisulfite is chosen as the reducing agent for acidic cleaning agents, and sodium sulfite is chosen as the reducing agent for alkaline cleaning agents. Adding a reducing agent reacts with residual hypochlorite ions in the water, preventing these highly oxidizing ions from damaging the reverse osmosis membrane structure and causing irreversible damage. Therefore, the pH of the reverse osmosis membrane cleaning agent needs to be matched with the reducing agent. Selecting the appropriate reducing agent based on its acidity or alkalinity provides a certain degree of bactericidal effect.

[0012] Preferably, the acidic cleaning agent formulation uses lysozyme. The alkaline cleaning agent mixture uses a combination of lipase and alkaline protease.

[0013] Lysozyme effectively lyses and inhibits bacteria by hydrolyzing their cell walls. Lipase can act on the ester bonds of triglycerides and other substances that are difficult to be washed away by surfactants. Alkaline protease is the most widely used enzyme preparation in liquid detergents and can specifically remove proteins present in extracellular polymers. The combination of the two can effectively disintegrate the structure of biological membranes.

[0014] Preferably, sodium benzoate is selected as the non-oxidizing bactericide in the acidic cleaning agent formulation, and benzalkonium chloride is selected in the alkaline cleaning agent formulation.

[0015] Sodium benzoate is weakly acidic, interfering with cell membrane permeability and inhibiting the activity of intracellular respiratory enzymes to achieve a bactericidal effect. Its effect is mild and suitable for use in cleaning reverse osmosis membranes. Benzalkonium chloride, as a cationic surfactant, is a non-oxidizing bactericide with broad-spectrum and highly efficient bactericidal and algicidal capabilities. It effectively controls the proliferation of bacteria and algae and the growth of slime in water, and has good slime-removing properties, as well as some dispersing and penetrating effects. It also has certain degreasing, deodorizing, and corrosion-inhibiting properties. Preferably, the acid-base cleaning agent formulation of this invention includes the following components:

[0016] Acidic cleaning agent formula: 1% tetrasodium EDTA, 5% sodium bisulfite, 2.5% lysozyme, 2% sodium benzoate.

[0017] Alkaline cleaning agent formula: 1% EDTA tetrasodium acetate, 5% sodium sulfite, 2.5% lipase, 2.5% alkaline protease, 2% benzalkonium chloride.

[0018] It is important to note that when prepared according to this formula, the pH of the acidic and alkaline cleaning agents will be within the suitable pH range for all three enzymes. If the dosage of the agents is increased or decreased, the pH range must be carefully controlled. The optimal operating temperature for the acidic and alkaline cleaning agents is 37℃.

[0019] In summary, compared with existing technologies, the above-described technical solutions conceived in this invention, by combining bioactive hydrolytic enzymes with non-oxidizing bactericides within different pH ranges, have the following innovative features:

[0020] (1) For different cleaning purposes, non-oxidizing bactericides suitable for acidic and alkaline cleaning are formulated. Sodium benzoate and benzalkonium chloride have good application prospects in the field of removing reverse osmosis membrane fouling.

[0021] (2) Alkaline washing uses sodium sulfite, a weakly alkaline reducing agent. While reducing hypochlorite ions, the alkaline environment is conducive to the removal of biological fouling from the reverse osmosis membrane.

[0022] (3) The acid and alkali cleaning agents are selected from non-oxidizing bactericides and enzymes, so that the bactericides kill bacteria and the enzymes break down the biofilm structure.

[0023] (4) In combination with the main targets of acid washing and alkaline washing, lysozyme is added to the acidic cleaning agent to enhance the bactericidal effect. Preferably, lipase and alkaline protease are added to the alkaline cleaning agent to further break down the biofilm structure and improve the overall membrane fouling control effect.

[0024] (5) Provide two sets of reverse osmosis membrane cleaning agent formulations with comprehensive cleaning functions;

[0025] (6) It can clean the contaminated membrane with very little reagent, which is low cost and high efficiency. Attached Figure Description

[0026] Figure 1 A comparison of the biofilm removal capabilities of different proteases.

[0027] Figure 2 This is a comparison chart showing the biofilm removal capabilities of acidic cleaning agents with different compositions.

[0028] Figure 3 This is a comparison chart showing the biofilm removal capabilities of alkaline cleaning agents with different compositions. Detailed Implementation

[0029] To better understand the above-mentioned objectives, features, and advantages of this invention, further experimental demonstrations will be conducted below. From a laboratory simulation perspective, strains screened from a contaminated reverse osmosis membrane were used to conduct experiments on the membrane resistance control effects of different formulations of cleaning agents. Specific experimental methods and evaluation indicators are as follows:

[0030] (1) Experimental methods

[0031] Biofilms were cultured using a 96-well plate culture method with a strain OD600 of 0.1 for 48 hours, with the culture medium being changed every 12 hours. Biofilms cultured using this method have a stable structure and can, to some extent, characterize the actual reverse osmosis membrane fouling situation.

[0032] (2) Optimal selection of alkaline enzymes

[0033] Enzymes that function in an alkaline environment mainly include alkaline proteases, trypsin, and keratinase. As mentioned above, an alkaline environment has advantages in removing biological contaminants. This patent optimizes the selection of alkaline proteases, trypsin, and keratinase. The four prepared enzyme preparations were added to the above-mentioned cultured biofilm system, and the treatment effects were compared after 1 hour.

[0034] (3) Preparation of acid and alkaline cleaning agents

[0035] First, the pH of the formulation system (Table 1-2) is adjusted to the appropriate pH range for the enzyme using weak acid and weak alkaline agents such as sodium bisulfite in the formulation. Then, enzyme components are added according to the sample amount. The enzyme components added here are the enzymes selected in step (2), and the reaction is carried out at 37°C for 1 hour.

[0036] Table 1-2 shows the different cleaning agent compositions used to verify the optimal cleaning agent formulation:

[0037] Table 1: Formulations of different agents in the acidic group

[0038]

[0039] Table 2: Formulations of different reagents in the alkaline group

[0040]

[0041] (4) Selection of the optimal alkaline enzyme

[0042] As attached Figure 1 As shown, the protein content of the loose layer and the firm layer of the biofilm system was measured after treatment with different enzymes. The combination of lipase and trypsin resulted in the lowest protein content in the firm layer, but the highest protein content in the loose layer among the four enzyme formulations. The combination of lipase and alkaline protease resulted in a slightly higher protein content in the firm layer than the combination of lipase and trypsin alone, but a lower protein content in the loose layer. Therefore, considering the cleaning effect of the four enzyme formulations, the combination of lipase and alkaline protease was selected.

[0043] (5) Evaluation indicators of pharmaceutical formulation

[0044] Biomass determination: The biomass contained in the biofilm after cleaning with different formulations of cleaning agents was determined by crystal violet staining. This included live and dead bacteria, proteins, polysaccharides, and other negatively charged biomass. This indicator represents the cleaning effect of the cleaning agent on the extracellular polymer components of the biofilm. (See attached...) Figure 2 Appendix Figure 3 It can be seen that the addition of enzymes effectively reduced biofilm biomass. After cleaning with both acidic and alkaline cleaning agents, the biomass was reduced by more than half, indicating that the enzyme components can effectively remove extracellular polymeric substances from the biofilm. The biofilm biomass in both acidic and alkaline groups ④ were significantly different from the control group (p < 0.05).

[0045] Bacterial abundance assay: This assesses the effectiveness of the formulation in removing bacteria. Biofilms, after treatment with different acidic cleaning agents, show the following characteristics: Figure 2 As shown, group ④ of acidic solutions exhibited the best bactericidal effect, indicating that the combination of sodium benzoate and lysozyme is more effective than either agent alone in terms of bactericidal action. After treatment with different alkaline cleaning agents, the biofilm showed the following... Figure 3 As shown, the alkaline group ④ has the best bactericidal effect, that is, the bactericidal effect is best when alkaline protease, lipase and benzalkonium chloride are combined.

[0046] (6) Evaluation of cleaning agent effectiveness

[0047] The improved acid-base cleaning agent formulation, which focuses on sterilization and removal of extracellular polymers in biofilms, shows, through experimental results (Table 3), that the combination of non-oxidizing bactericides and bioactive hydrolytic enzymes has both bactericidal effect and can remove most of the biomass.

[0048] Table 3: Overview of the membrane fouling removal capabilities of acidic and alkaline cleaning agents with different compositions

[0049]

[0050] In summary, this invention successfully improved the formulation of common acid and alkali cleaning agents for reverse osmosis membranes. Based on the design concept of sterilization and destruction of biofilm structure, and combined with different pH cleaning environments, the improved formulation is formulated with non-oxidizing bactericides and bioactive hydrolytic enzymes. The experimental results all show that the improved formulation has a good effect in controlling reverse osmosis membrane fouling, indicating that the improved formulation has potential value in membrane fouling control.

[0051] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A reverse osmosis membrane cleaning agent composed of a non-oxidizing bactericide and a bioactive hydrolytic enzyme, characterized in that, The cleaning agents include acidic and alkaline cleaning agents; depending on the type of reverse osmosis membrane fouling, alternating acid and alkaline cleaning or one of them may be selected. Based on 100% of the total mass of the cleaning agent, the acidic cleaning agent includes the following components: 1%-10% metal chelating agent, 1%-10% reducing agent, 0.5%-10% bioactive enzyme, 1%-10% non-oxidizing bactericide, and the balance being water; Based on 100% of the total mass of the cleaning agent, the alkaline cleaning agent includes the following components: 1%-10% metal chelating agent, 1%-10% reducing agent, 0.5%-10% mixed bioactive enzymes, 1%-10% non-oxidizing bactericide, and the balance being water; in, In the formulations of acidic and alkaline cleaning agents, the metal chelating agent is tetrasodium ethylenediaminetetraacetate; The reducing agent in acidic cleaning agents is sodium bisulfite, and the reducing agent in alkaline cleaning agents is sodium sulfite; The bioactive hydrolytic enzyme in acidic cleaning agents is lysozyme, while the bioactive hydrolytic enzyme in alkaline cleaning agents is a combination of lipase and alkaline protease. In acidic cleaning agents, the non-oxidizing bactericide is sodium benzoate, while in alkaline cleaning agents it is benzalkonium chloride.

2. The cleaning agent according to claim 1, characterized in that, Acidic cleaning agent formula: 1% tetrasodium EDTA, 5% sodium bisulfite, 2.5% lysozyme, 2% sodium benzoate, balance water; Alkaline cleaning agent formula: 1% EDTA tetrasodium, 5% sodium sulfite, 2.5% lipase, 2.5% alkaline protease, 2% benzalkonium chloride, balance water.

3. The application of the cleaning agent according to claim 1 or 2 for cleaning reverse osmosis membranes.

4. In the application according to claim 3, depending on the degree of reverse osmosis membrane fouling, alternating acid and alkali cleaning or one of them can be selected.

5. In the application according to claim 3, the cleaning agent is used at a temperature of 37°C.

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