A method of cleaning a reverse osmosis membrane module
By using a combination of solutions A and B, the problem of complex pollution in mine water was solved, achieving efficient cleaning of reverse osmosis membrane modules, increasing membrane flux and extending service life, while avoiding the side effects of chemical agents.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHENHUA SHENDONG COAL GRP
- Filing Date
- 2026-04-07
- Publication Date
- 2026-06-19
Smart Images
Figure CN122230538A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of membrane cleaning or disinfection technology, and more particularly to a method for cleaning reverse osmosis membrane modules. Background Technology
[0002] Reverse osmosis technology, as a core process in water purification and material concentration, is widely used in municipal water supply, seawater desalination, industrial wastewater treatment, and food and beverage processing due to its high efficiency in removing pollutants. However, during long-term operation, reverse osmosis systems are prone to biofilm fouling due to factors such as fluctuations in feed water quality and suitable temperature and humidity in the operating environment. This can lead to the growth of bacteria, fungi, algae, and other microorganisms on the surface and within the flow channels of the membrane modules. This not only results in decreased membrane flux and increased energy consumption but may also cause deterioration of the product water quality and even irreversible damage to the membrane materials, seriously affecting the stable operation of the reverse osmosis system.
[0003] Currently, the main approach to treating microbial contamination in reverse osmosis systems is through periodic chemical cleaning combined with online sterilization. Commonly used chemical agents include chlorine-based oxidants and peroxides, which, while inhibiting microbial growth in the short term, have significant limitations: firstly, excessive chemical agents can react with organic matter in the water to generate toxic byproducts, increasing the difficulty of subsequent treatment; secondly, long-term use can lead to drug resistance in microorganisms, and it is difficult to completely remove biofilms adhering to the membrane surface, resulting in a gradually shortening cleaning cycle and accelerated membrane lifespan decline. However, the above cleaning methods are mainly suitable for conventional water qualities such as municipal wastewater and industrial circulating water, and are unsuitable for special contamination scenarios such as mine water with high hardness (calcium and magnesium scale), high suspended solids (coal dust, silt), and high microbial density (anaerobic bacteria). The high hardness of mine water easily leads to stubborn inorganic scale contamination, and the anaerobic environment of mine water also easily causes repeated biofilm growth, seriously affecting the stable operation of the reverse osmosis system. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a cleaning method for reverse osmosis membrane modules.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for cleaning a reverse osmosis membrane module, comprising the following steps: S1. Backwash the reverse osmosis membrane module; S2. Immerse the reverse osmosis membrane module after step S1 in solution A. S3. Use solution A to backwash the reverse osmosis membrane module after step S2. S4. Immerse the reverse osmosis membrane module after step S3 in solution B. S5. Use solution B to backwash the reverse osmosis membrane module after step S4. Solution A consists of the following components in the indicated mass concentrations: 0.05%~0.3% acid, 0.4%~0.6% ethylenediaminetetraacetic acid (EDTA), 0.01%~0.1% polyacrylic acid (PAA), with the remainder being water; Solution B consists of the following components in the indicated mass concentrations: 0.005%~0.05% isothiazolinone, 0.05%~0.2% sodium dihydrogen phosphate, and the remainder is water.
[0006] To address the complex fouling caused by high suspended solids, inorganic scale, and biofilm in mine water, this invention employs a series of physical pre-rinsing, A-solution soaking and backwashing, and B-solution soaking and backwashing processes on the reverse osmosis membrane module. The A-solution utilizes acid to dissolve surface scale, ethylenediaminetetraacetic acid to chelate deep metal ions to prevent scale redeposition, and polyacrylic acid to inhibit scale dispersion, achieving efficient removal and prevention of deep scale redeposition. Subsequently, the B-solution utilizes isothiazolinone to penetrate the biofilm and kill deep microorganisms, thus solving the problem of repeated biofilm growth in the anaerobic environment of mine water. This improves sterilization stability, extends the membrane fouling rebound cycle, and ultimately achieves efficient removal of complex biofilm fouling, increases membrane flux recovery rate, reduces membrane module damage, and extends membrane lifespan.
[0007] To achieve optimal cleaning results, strong acidic (pH < 1) or strong alkaline (pH > 12) agents, or high-concentration oxidizing bactericides, are commonly used. These methods can exacerbate membrane corrosion in the high-chloride environment of mine water (e.g., hydrolysis of polyamide membranes, irreversible shrinkage of membrane pores), leading to a shortened membrane element replacement cycle to 1-2 years. Furthermore, some bactericides react with high-chloride water to produce toxic byproducts, increasing the burden on subsequent treatment processes. In this invention, solution A has a low acid concentration, solution B is a neutral system (isothiazolinone has no side reactions with high-chloride water), and no strong oxidizing agents are used throughout the process. Simultaneously, the soaking and backwashing methods avoid a sudden increase in membrane surface pressure, reducing mechanical damage. Moreover, no toxic byproducts are generated after cleaning, allowing for seamless integration with subsequent zero-discharge processes without additional treatment, thus reducing the burden of secondary pollution.
[0008] Moreover, compared to existing scale inhibitors / cleaning agents, which often require multiple chemical modifications (such as silane coupling agent modification and organic solvent extraction), strict temperature control (50~60℃) or long reaction times (4~6 hours), resulting in complex preparation processes and high raw material costs (such as specialized chelating agents and imported bactericides), the A / B solutions in this invention only require stirring and dissolving at room temperature (≤20 minutes). No specialized equipment is needed, and they can be prepared on-site immediately. This not only significantly reduces costs but also reduces reliance on specialized equipment and energy consumption, meeting the immediate on-site cleaning needs of mines.
[0009] In some embodiments, the mass concentration of acid in solution A may be, but is not limited to, a range of any one or any two of the following: 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, and 0.3%.
[0010] In some embodiments, the mass concentration of ethylenediaminetetraacetic acid (EDTA) in solution A can be, but is not limited to, any or both of the following values: 0.4%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, 0.5%, 0.51%, 0.52%, 0.53%, 0.54%, 0.55%, 0.56%, 0.57%, 0.58%, 0.59%, and 0.6%. Compared to other chelating agents, EDTA has more effective chelating sites and better stability. When combined with acids and polyacrylic acid, it can achieve higher chelation efficiency, thereby achieving better cleaning results.
[0011] In some embodiments, the mass concentration of polyacrylic acid in solution A can be, but is not limited to, any or both of the following ranges: 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, and 0.1%. Compared to other scale inhibitors, polyacrylic acid exhibits higher stability in strongly acidic systems and, when combined with acids and ethylenediaminetetraacetic acid, achieves better cleaning results.
[0012] In some embodiments, the molecular weight of polyacrylic acid is preferably in the range of 1,000 to 10,000, for example, but not limited to any one or both of the following values: 1,000, 1,500, 2,000, 2,500, 3,000, 3,500, 4,000, 4,500, 5,000, 5,500, 6,000, 6,500, 7,000, 7,500, 8,000, 8,500, 9,000, 9,500, and 10,000.
[0013] In some embodiments, the water in solution A is preferably deionized water, distilled water, ultrapure water, etc.
[0014] In some embodiments, the preferred mass concentration of isothiazolinone in solution B is within the range of any one or both of the following: 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, and 0.05%. Compared to other bactericides, using isothiazolinone as the core bactericidal component can penetrate the biofilm on the surface of the reverse osmosis membrane to kill deep-seated hidden microorganisms, effectively solving the problem of repeated biofilm growth in anaerobic environments of mine water, and providing long-term inhibition of microbial contamination rebound.
[0015] In some embodiments, the preferred mass concentration of sodium dihydrogen phosphate in solution B is within the range of any one or both of the following: 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, and 0.2%. Sodium dihydrogen phosphate acts as a pH buffer in the system, stabilizing the acid-base environment of solution B to ensure that isothiazolinone maintains optimal bactericidal activity over a long period. Simultaneously, it helps chelate residual metal ions in the system, reducing the risk of scale redeposition and membrane material damage.
[0016] In some embodiments, the water in solution B is preferably deionized water, distilled water, ultrapure water, etc.
[0017] In a preferred embodiment of the cleaning method for the reverse osmosis membrane module of the present invention, the pressure of the backwashing process in step S1 is 5 bar to 10 bar.
[0018] In some implementations, the pressure of the backwashing process in step S1 may be, but is not limited to, any or both of the following values: 5 bar, 6 bar, 7 bar, 8 bar, 9 bar, 10 bar.
[0019] In a preferred embodiment of the cleaning method for the reverse osmosis membrane module of the present invention, the backwashing time in step S1 is 5 min to 15 min.
[0020] In some embodiments, the backwashing time in step S1 may be, but is not limited to, any or both of the following: 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, and 15 min.
[0021] In a preferred embodiment of the cleaning method for the reverse osmosis membrane module of the present invention, the soaking time in step S2 is 0.5h to 3h.
[0022] In some embodiments, the soaking time in step S2 may be, but is not limited to, any one or any two of 0.5h, 1h, 1.5h, 2h, 2.5h, and 3h.
[0023] In a preferred embodiment of the cleaning method for the reverse osmosis membrane module of the present invention, the pressure of the backwashing process in step S3 is 5 bar to 10 bar.
[0024] In some implementations, the pressure of the backwashing process in step S3 may be, but is not limited to, any or both of the following values: 5 bar, 6 bar, 7 bar, 8 bar, 9 bar, 10 bar.
[0025] In a preferred embodiment of the cleaning method for the reverse osmosis membrane module of the present invention, the backwashing time in step S3 is 1 hour to 3 hours.
[0026] In some implementations, the backwashing time in step S3 may be, but is not limited to, any one or both of 1h, 1.5h, 2h, 2.5h, and 3h.
[0027] In a preferred embodiment of the cleaning method for the reverse osmosis membrane module of the present invention, the soaking time in step S4 is 0.5h to 3h.
[0028] In some embodiments, the soaking time in step S4 may be, but is not limited to, any one or any two of 0.5h, 1h, 1.5h, 2h, 2.5h, and 3h.
[0029] In a preferred embodiment of the cleaning method for the reverse osmosis membrane module of the present invention, the backwashing pressure in step S5 is 5 bar to 10 bar.
[0030] In some implementations, the pressure of the backwashing process in step S5 may be, but is not limited to, any or both of the following values: 5 bar, 6 bar, 7 bar, 8 bar, 9 bar, 10 bar.
[0031] In a preferred embodiment of the cleaning method for the reverse osmosis membrane module of the present invention, the backwashing time in step S5 is 1 hour to 3 hours.
[0032] In some implementations, the backwashing time in step S5 may be, but is not limited to, any one or both of 1h, 1.5h, 2h, 2.5h, and 3h.
[0033] In a preferred embodiment of the cleaning method for the reverse osmosis membrane module of the present invention, the acid in the solution A includes at least one of hydrochloric acid, nitric acid, acetic acid, tartaric acid, and citric acid.
[0034] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention addresses the problem of repeated biofilm growth in anaerobic mine water by sequentially performing physical pre-rinsing, A-solution immersion and backwashing, and B-solution immersion and backwashing on the reverse osmosis membrane module. The A-solution utilizes acid to dissolve surface scale, ethylenediaminetetraacetic acid to chelate deep metal ions to prevent scale redeposition, and polyacrylic acid to inhibit scale dispersion, achieving efficient removal and prevention of deep scale redeposition. Subsequently, the B-solution utilizes isothiazolinone to penetrate the biofilm and kill deep microorganisms, thus solving the problem of repeated biofilm growth in anaerobic mine water environments. This improves sterilization stability, extends the membrane fouling rebound cycle, and ultimately achieves efficient removal of complex biofilm fouling, increases membrane flux recovery rate, reduces membrane module damage, and extends membrane lifespan. Attached Figure Description
[0035] Figure 1 The images show SEM images of the membrane module surface before and after cleaning in Example 1. Detailed Implementation
[0036] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.
[0037] Unless otherwise specified, all other materials and reagents used in the examples are commercially available.
[0038] The membrane used in the experiment was an industrial-grade polyamide composite reverse osmosis membrane with an initial flux of 30 LMH and an initial desalination rate of ≥99%.
[0039] The experimental water was mine water (water quality indicators are shown in Table 1) and derived working condition water.
[0040] Table 1. Main water quality indicators of the mine water used in the experiment
[0041] Example 1 (High salinity water: water quality shown in Table 1) A reverse osmosis system in a mining plant experienced a continuous 35% drop in membrane flux. Testing confirmed the presence of a biofilm on the membrane surface (primarily composed of Pseudomonas bacteria, with a total bacterial count reaching 10). 6 CFU cm -2 (Bacterial activity exceeding 70%) and complex contamination with colloids and organic matter require sterilization and cleaning treatment.
[0042] A method for cleaning a reverse osmosis membrane module includes the following steps: (1) Backwash the fouled membrane module with high-pressure clean water (5 bar) for 10 minutes to remove loose pollutants; (2) Mix 0.1% nitric acid, 0.5% ethylenediaminetetraacetic acid (EDTA), 0.05% polyacrylic acid (PAA) and the remainder deionized water, and stir magnetically for 15 minutes until all components are dissolved to obtain solution A; The membrane module after step (1) is immersed in solution A and soaked at room temperature for 1 hour; after soaking, the membrane module is backwashed (5 bar) with solution A for 1 hour. (3) Mix isothiazolinone with a mass concentration of 0.02%, sodium dihydrogen phosphate with a mass concentration of 0.1%, and the remainder deionized water, and stir magnetically for 10 minutes until all components are dissolved; The membrane module after step (2) is immersed in solution B and soaked at room temperature for 1 hour; after soaking, the membrane module is backwashed (5 bar) with the above solution B for 1 hour.
[0043] After cleaning, the membrane module flux recovered to 98.6% of its initial value, and the membrane surface sterilization rate was 99%; simultaneously, according to Figure 1 As can be seen from a and b (the contaminated membrane surface) and c (the cleaned membrane surface), the contaminants on the membrane surface were cleaned and the membrane was not significantly damaged.
[0044] Example 2 (High PAM mine water quality: Water quality shown in Table 1 + PAM-2mg / L) Fouling status of reverse osmosis membrane modules: membrane flux decreased by 40% from the initial flux, desalination rate <95%, membrane surface contains PAM colloids and biofilm.
[0045] A method for cleaning a reverse osmosis membrane module includes the following steps: (1) Backwash the fouled membrane module with high-pressure clean water (5 bar) for 10 minutes to remove loose pollutants; (2) Mix 0.15% nitric acid, 0.5% ethylenediaminetetraacetic acid (EDTA), 0.05% polyacrylic acid (PAA) and the remainder deionized water, and stir magnetically for 15 minutes until all components are dissolved to obtain solution A; The membrane module after step (1) is immersed in solution A and soaked at room temperature for 1 hour; after soaking, the membrane module is backwashed (5 bar) with the above solution A for 1 hour. (3) Mix isothiazolinone with a mass concentration of 0.02%, sodium dihydrogen phosphate with a mass concentration of 0.1%, and the remainder deionized water, and stir magnetically for 10 minutes until all components are dissolved; The membrane module after step (2) is immersed in solution B and soaked at room temperature for 1 hour; after soaking, the membrane module is backwashed (5 bar) with the above solution B for 1 hour.
[0046] After cleaning, the membrane module flux recovered to 97.8% of the initial value, the membrane surface sterilization rate was 99%, and electron microscopy confirmed that there was no obvious damage to the membrane surface.
[0047] Example 3 (High salinity + high PAM mine water quality: Water quality shown in Table 1 + PAM-2mg / L + CaCl2, Ca²) + (Concentration of 120 mg / L) Fouling status of reverse osmosis membrane modules: membrane flux decreased by 40% from the initial flux, desalination rate <95%, and the membrane surface contains calcium scale, PAM and biofilm.
[0048] A method for cleaning a reverse osmosis membrane module includes the following steps: (1) Backwash the fouled membrane module with high-pressure clean water (5 bar) for 10 minutes to remove loose pollutants; (2) Mix 0.2% nitric acid, 0.5% ethylenediaminetetraacetic acid (EDTA), 0.05% polyacrylic acid (PAA) and the remainder deionized water, and stir magnetically for 15 minutes until all components are dissolved to obtain solution A; The membrane module after step (1) is immersed in solution A and soaked at room temperature for 1 hour; after soaking, the membrane module is backwashed (5 bar) with the above solution A for 1 hour. (3) Mix isothiazolinone with a mass concentration of 0.03%, sodium dihydrogen phosphate with a mass concentration of 0.1%, and the remainder deionized water, and stir magnetically for 10 minutes until all components are dissolved; The membrane module after step (2) is immersed in solution B and soaked at room temperature for 1 hour; after soaking, the membrane module is backwashed (5 bar) with the above solution B for 1 hour.
[0049] After cleaning, the membrane module flux recovered to 97.6% of the initial value, the membrane surface sterilization rate was 99%, and electron microscopy confirmed that there was no obvious damage to the membrane surface.
[0050] Comparative Example 1 A method for cleaning a reverse osmosis membrane module includes the following steps: (1) Backwash the fouled membrane module (same as in Example 1) with high-pressure clean water (5 bar) for 10 minutes to remove loose pollutants; (2) Mix hydrochloric acid with deionized water to obtain an acid washing solution with a pH of 2; immerse the membrane module treated in step (1) in the acid solution and soak it at room temperature for 1 hour; after soaking, backwash the membrane module with the above acid solution (5 bar) for 1 hour. (3) Sodium dodecylbenzenesulfonate with a mass concentration of 0.025%, sodium tripolyphosphate with a mass concentration of 1%, sodium hydroxide with a mass concentration of 0.2%, sodium polyacrylate with a mass concentration of 0.1%, and the balance deionized water are mixed evenly to obtain an alkaline washing solution. The membrane module after step (2) is immersed in alkaline washing solution and soaked at room temperature for 1 hour; after soaking, the membrane module is backwashed (5 bar) with the above alkaline solution for 1 hour.
[0051] After cleaning, the membrane module flux recovered to 93.4% of its initial value, and the membrane surface sterilization rate was 90%.
[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A method for cleaning a reverse osmosis membrane module, characterized in that, Includes the following steps: S1. Backwash the reverse osmosis membrane module; S2. Immerse the reverse osmosis membrane module after step S1 in solution A. S3. Use solution A to backwash the reverse osmosis membrane module after step S2. S4. Immerse the reverse osmosis membrane module after step S3 in solution B. S5. Use solution B to backwash the reverse osmosis membrane module after step S4. Solution A consists of the following components in the indicated mass concentrations: 0.05%~0.3% acid, 0.4%~0.6% ethylenediaminetetraacetic acid, 0.01%~0.1% polyacrylic acid, with the remainder being water; Solution B consists of the following components in the indicated mass concentrations: 0.005%~0.05% isothiazolinone, 0.05%~0.2% sodium dihydrogen phosphate, and the remainder is water.
2. The cleaning method as described in claim 1, characterized in that, The backwashing pressure in step S1 is 5 bar to 10 bar.
3. The cleaning method as described in claim 2, characterized in that, The backwashing process in step S1 takes 5 to 15 minutes.
4. The cleaning method as described in claim 1, characterized in that, The soaking time in step S2 is 0.5h to 3h.
5. The cleaning method as described in claim 1, characterized in that, The backwashing pressure in step S3 is 5 bar to 10 bar.
6. The cleaning method as described in claim 5, characterized in that, The backwashing process in step S3 lasts for 1 to 3 hours.
7. The cleaning method as described in claim 1, characterized in that, The soaking time in step S4 is 0.5h to 3h.
8. The cleaning method as described in claim 1, characterized in that, The backwashing pressure in step S5 is 5 bar to 10 bar.
9. The cleaning method as described in claim 8, characterized in that, The backwashing process described in step S5 takes 1 to 3 hours.
10. The cleaning method according to any one of claims 1 to 9, characterized in that, The acid in solution A includes at least one of hydrochloric acid, nitric acid, acetic acid, tartaric acid, and citric acid.