Membrane fouling mild cleaning method based on quorum sensing inhibition and habitat regulation

Abstract

The application provides a mild cleaning method for membrane pollution based on quorum sensing inhibition and habitat regulation. The method initiates a cleaning process when the operation parameters of the membrane system deviate from the set operation range, and performs quorum sensing inhibition mild cleaning on the membrane. During the cleaning process, low-intensity acid and alkali pre-cleaning is selectively introduced according to the operation state of the membrane system. After the cleaning is completed, the cleaning state is judged according to the operation parameters of the membrane system until the operation parameters of the membrane system return to the set operation range. During the cleaning process, the quorum sensing inhibition interferes with the microbial quorum sensing signal transmission in the membrane pollution layer, weakens the effect of extracellular polymeric substances on the structural stability of the pollution layer, and changes the survival conditions of the microorganisms in the membrane pollution layer through habitat regulation, so as to loosen and peel off the membrane pollution layer formed by biological pollution, organic pollution, inorganic pollution or their combination under non-caustic conditions. The method avoids the use of strong oxidizing bactericides and is suitable for pollution control and cleaning process of different types of membrane systems.

Description

Technical Field

[0001] This invention relates to the fields of water treatment and membrane separation technology, specifically to a mild membrane fouling cleaning method and its matching cleaning agent that achieves membrane fouling layer removal and membrane system operating parameter restoration under mild chemical conditions based on swarm suppression and habitat regulation. Background Technology

[0002] Membrane separation technology is widely used in industrial wastewater treatment, water reuse, and the reduction of high-salinity wastewater. During long-term operation, membrane systems are prone to gradually forming a fouling layer on the membrane surface and within the membrane pore structure, composed of inorganic deposits, organic matter, and microbial components. This type of membrane fouling typically presents as a complex mixture of inorganic, organic, and biological fouling, as well as multiple types of fouling. Among these, biological fouling and its coupling with organic and inorganic fouling have a significant impact on membrane flux decline and operational stability. The coupling characteristics of multi-component fouling not only lead to a decrease in membrane flux and an increase in operating pressure differential, but also shorten the stable operating cycle of the membrane system.

[0003] To address membrane fouling, existing technologies typically employ acidic or alkaline cleaning methods to remove the fouling layer. To improve removal efficiency, high-intensity acid and alkali cleaning conditions are often used in practical engineering applications. However, under repeated operation and cleaning cycles, strong chemical cleaning conditions can easily alter the structural characteristics of the membrane fouling layer, causing it to gradually become denser, thus reducing the effectiveness of subsequent cleaning. Furthermore, membrane materials may experience performance degradation under long-term strong chemical conditions, ultimately affecting the continuous and stable operation of the membrane system.

[0004] Furthermore, in actual engineering operations, it has been found that repeated use of strong acid and alkali cleaning methods not only fails to fundamentally improve membrane fouling, but may also have a screening effect on the microbial community structure within the fouled layer during multiple cleaning cycles. Strong acid and alkali cleaning preferentially removes chemically sensitive fouling components and individual microorganisms, while having a relatively limited impact on microorganisms that can maintain structural stability through the secretion of large amounts of extracellular polymers. This results in microorganisms with high extracellular polymer secretion capacity and stronger environmental tolerance gradually becoming dominant in the residual fouled layer after cleaning. The fouled layer formed by these microorganisms typically has higher adhesion and structural stability, and is more likely to rapidly recombine organic and inorganic deposits during subsequent operation, further enhancing the membrane fouling potential. This process makes traditional caustic cleaning methods increasingly difficult to clean with repeated operation and cleaning cycles, and its dependence on high-intensity acid and alkali conditions gradually intensifies, increasing the difficulty of membrane system operation and maintenance and the long-term cost burden.

[0005] To improve the cleaning effect of biofouling, some technical solutions introduce bactericides or oxidizing agents into the cleaning system to treat microorganisms on the membrane surface. For example, Chen Hong et al. (Authorization Announcement No.: CN117504603B) disclosed a reverse osmosis membrane cleaning agent composed of a non-oxidizing bactericide and an enzyme, and its application. This removes biofouling from the membrane surface through the synergistic effect of the non-oxidizing bactericide and the bioactive hydrolytic enzyme. This type of technology primarily relies on microbial killing or enzymatic hydrolysis of biomolecules, and the cleaning process still requires an acidic or alkaline cleaning stage, making it difficult to control the stability of the composite fouling layer at the overall structural level. In addition, some technologies attempt to regulate membrane fouling from the perspective of fouling formation mechanisms. Yu Huarong et al. (Application Publication No.: CN118026399A) disclosed a quorum quenching composite stimulant and a membrane fouling control method based on it. By adding a quorum quencher to the reactor, the concentration of microbial quorum sensing signal molecules is reduced, thereby inhibiting the secretion of extracellular polymers and slowing down membrane fouling formation. This type of technology mainly applies to the fouling control stage during membrane system operation and does not address the cleaning process after membrane fouling occurs. Furthermore, Tan Xuejie et al. (application publication number: CN120586658A) disclosed a highly efficient and environmentally friendly antiscaling cleaning agent for reverse osmosis membranes based on a composite formulation and its preparation method. This agent removes membrane fouling through the synergistic effect of composite surfactants, organic acids, and slow-release components. This type of technology primarily weakens the fouling layer structure through the chemical dissolution, dispersion, or complexation of the components in the formulation. Its cleaning effect still depends on the chemical detergency of the cleaning agent itself and the strength of the formulation, and does not involve technical approaches that modify the overall stability of the fouling layer by regulating the behavior of microbial communities or the formation mechanism of extracellular polymers within the fouling layer.

[0006] In summary, existing technologies primarily utilize quorum sensing suppression or quenching techniques for membrane fouling prevention or operational control, while membrane cleaning technologies still mainly rely on acid-base cleaning, bactericides, or enzyme preparations. Further research is needed to determine how to introduce quorum sensing suppression into the membrane fouling cleaning process without relying on caustic chemical conditions or microbial eradication, thereby achieving controllable weakening and removal of the complex fouling layer structure while maintaining stable membrane system operating parameters. Summary of the Invention

[0007] The purpose of this invention is to provide a mild membrane fouling cleaning method and its matching cleaning agent based on swarm inhibition and habitat regulation. Without relying on high-intensity chemical conditions or strong oxidizing bactericides, this method can effectively weaken and remove the membrane fouling layer structure, slow down the decline in cleaning efficiency, and maintain the stability of membrane system operating parameters.

[0008] To achieve the above objectives, the present invention provides a gentle membrane fouling cleaning method based on swarm immunity suppression and habitat regulation, comprising the following steps:

[0009] (1) During the operation of the membrane system, when membrane fouling causes the membrane system operating parameters to deviate from the set operating range, the cleaning process is initiated;

[0010] (2) After starting the cleaning process, determine whether low-intensity acid-base pre-cleaning is required based on the current operating status of the membrane system; if low-intensity acid-base pre-cleaning is required, perform low-intensity acid-base pre-cleaning on the membrane; if low-intensity acid-base pre-cleaning is not required, proceed directly to the swarm suppression mild cleaning step.

[0011] (3) When entering the quorum suppression mild cleaning step, apply a mild cleaning agent containing quorum inhibitor to the membrane to perform quorum suppression mild cleaning.

[0012] (4) After completing the swarm suppression and mild cleaning, the cleaning status is determined based on the membrane system operating parameters; if the membrane flux has not recovered to the set operating range, the process returns to perform low-intensity acid and alkali pre-cleaning and swarm suppression and mild cleaning in sequence; if the membrane system operating parameters recover to the set operating range, the cleaning process ends.

[0013] The low-intensity acid-base pre-cleaning includes low-intensity acidic pre-cleaning and low-intensity alkaline pre-cleaning. The pH of the cleaning solution for the low-intensity acidic pre-cleaning is 3.5 to 6.5, and the pH of the cleaning solution for the low-intensity alkaline pre-cleaning is 9.0 to 11.5. During the low-intensity acid-base pre-cleaning and swarm suppression mild cleaning processes, the cleaning temperature does not exceed 40°C. Under this temperature condition, thermal damage to the membrane material and secondary densification of the fouling layer structure are not caused, and the cleaning effect is not significantly affected.

[0014] The cleaning agent used for the mild cleaning of the swarm suppression comprises, by weight percentage, 0.001% to 1.0% swarm suppressant, 0.05% to 1.0% buffer, 0% to 5.0% alcohol co-solvent, and the balance being deionized water, wherein the swarm suppressant is a non-in vivo chemical substance.

[0015] The swarm inhibitor is selected from one or more of lactones, esters, aromatic aldehydes, aromatic phenols, indoles, polyphenols, flavonoids, or their derivatives.

[0016] The swarm inhibitors include one or more of the following: γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, aliphatic lactone derivatives, thymol, eugenol, isoeugenol, vanillin, cinnamaldehyde, carvacrol, green tea polyphenols, epigallocatechin gallate, curcumin, indole, or derivatives thereof.

[0017] The buffer is used to adjust and maintain the acid-base stability of the cleaning system, and can be selected from commonly used buffer systems in the art, including but not limited to phosphate buffer systems, carbonate buffer systems, borate buffer systems, or combinations thereof.

[0018] The cleaning agent does not contain strong oxidizing bactericides. During the preparation of the cleaning agent, the susceptibility inhibitor is preferably first dissolved in an alcohol-based co-solvent to form a homogeneous pre-solution, and then the pre-solution and buffer are added together to deionized water and mixed thoroughly to obtain the cleaning agent.

[0019] The cleaning agent, after being diluted with water to form a cleaning solution, is used to perform a gentle cleaning of the membrane by inhibiting swarming. The swarming inhibitor has a mass concentration of 10 mg / L to 100 mg / L in the cleaning solution. Its cleaning effect mainly comes from the regulation of the fouling layer structure and microbial habitat conditions by the swarming inhibitor, rather than from achieving fouling removal by increasing acid-base strength or oxidizing power.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] 1. By limiting the parameters of low-intensity acid and alkali pre-cleaning and combining them with a mild cleaning step to suppress swarming, the chemical intensity of the cleaning process is significantly reduced while meeting the initial loosening requirements of the fouling layer. This reduces the risk of structural damage and performance degradation of the membrane material under repeated cleaning conditions, which is beneficial to extending the effective service life of the membrane module.

[0022] 2. Introducing quorum sensing inhibitors during the mild cleaning phase does not aim to kill microorganisms, but rather weakens the formation of extracellular polymers and their enhancing effect on the structural stability of the contamination layer by interfering with the transmission of quorum sensing signals of microorganisms within the contamination layer. This reduces the dependence on strong acid, strong alkali, or strong oxidizing cleaning agents from a mechanistic perspective, thereby significantly reducing the frequency and dosage of traditional cleaning agents under multiple cleaning cycles.

[0023] 3. By regulating the microbial habitat and structural state of the contamination layer through swarm inhibitors, the contamination layer formed by biological, organic, inorganic, or composite contamination is more likely to loosen and peel off under non-caustic chemical conditions, thereby achieving effective removal of the contamination layer and avoiding the traditional approach of simply relying on increasing acid or alkali strength or oxidizing power to achieve cleaning.

[0024] 4. Under repeated contamination and cleaning cycles, the method of this invention is beneficial to maintaining the long-term stability of membrane system operating parameters. Compared with traditional strong acid and strong alkali cleaning methods, it can extend the operating cycle, reduce the cleaning frequency, and reduce cleaning downtime and reagent consumption under the same flux reduction conditions, thereby significantly reducing the operating and maintenance costs of the membrane system. It has good engineering applicability and economy. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a mild membrane fouling cleaning method based on swarm immunity suppression and habitat regulation.

[0026] Figure 2 This is a comparison chart of the membrane cleaning efficiency of the cleaning methods in Example 1 and Comparative Example 1 under multiple cleaning conditions;

[0027] Figure 3 The images show a comparison of the membrane surface contamination layer before and after cleaning in Example 1 and Comparative Example 1, where (a) is the membrane surface contamination layer before cleaning in Example 1, (b) is the membrane surface contamination layer after cleaning in Example 1, (c) is the membrane surface contamination layer before cleaning in Comparative Example 1, and (d) is the membrane surface contamination layer after cleaning in Comparative Example 1.

[0028] Figure 4 The images show a comparison of electron microscopy morphology of the contaminant layer on the membrane surface after cleaning using the cleaning methods of Example 1 and Comparative Example 1, where (a) is the microscopic morphology of the membrane surface after cleaning in Example 1, and (b) is the microscopic morphology of the membrane surface after cleaning in Comparative Example 1.

[0029] Figure 5 The graph shows the change in biomass on the membrane surface before and after cleaning according to the cleaning methods of Example 1 and Comparative Example 1.

[0030] Figure 6 The graph shows the changes in the content of inorganic contaminants on the membrane surface before and after cleaning in Example 1 and Comparative Example 1. Detailed Implementation

[0031] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0032] The present invention will be further described below with reference to the embodiments and accompanying drawings. It should be noted that the following 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.

[0033] like Figure 1 As shown, the present invention provides a mild membrane fouling cleaning method based on swarm immunity suppression and habitat regulation, comprising the following steps.

[0034] S100. Start

[0035] The membrane system is in normal operation, and the system performs filtration or separation operations according to the set operating parameters.

[0036] S200. Membrane fouling occurs.

[0037] As the membrane system continues to operate, a membrane fouling layer gradually forms on the membrane surface and within the membrane pore structure, consisting of inorganic deposits, organic matter, and microbial-related components.

[0038] S300. Determine if operation is affected.

[0039] The operating status of the membrane system is monitored. When the membrane flux decreases, the operating pressure difference increases, or other operating parameters deviate from the set operating range, it is determined that membrane fouling has had an adverse effect on the operation of the membrane system. If no significant impact is observed, the membrane system continues to operate.

[0040] S400. Determine if pre-cleaning is required.

[0041] After confirming that membrane fouling is affecting operation, determine whether a low-intensity acid-base pre-cleaning step is necessary based on the degree of membrane fouling and changes in operating parameters. When the proportion of inorganic or organic deposits in the fouling layer is high, it can be determined that pre-cleaning is necessary. When the fouling layer is relatively loose or mainly composed of biological structures, pre-cleaning may not be necessary.

[0042] S500 Low-Intensity Acid / Alkali Pre-Clean

[0043] If pre-cleaning is deemed necessary, a low-intensity acid-base pre-cleaning is performed on the membrane. This low-intensity acid-base pre-cleaning includes both low-intensity acidic and low-intensity alkaline pre-cleaning. The pH of the cleaning solution for the low-intensity acidic pre-cleaning is controlled within the range of 3.5 to 6.5, and the pH of the cleaning solution for the low-intensity alkaline pre-cleaning is controlled within the range of 9.0 to 11.5. The temperature of the cleaning solution is controlled within the range of 15°C to 40°C, ensuring that the cleaning temperature is between 15°C and 40°C.

[0044] S600. Gentle Cleaning and Inhibition of Group Sensitivity

[0045] After completing a low-intensity acid-base pre-cleaning, or if it is determined that pre-cleaning is not necessary, a mild cleaning agent containing a quorum inhibitor is applied to the membrane to perform a quorum suppression mild cleaning. In this step, the cleaning effect mainly comes from the interference of the quorum inhibitor on the transmission of microbial quorum sensing signals within the membrane fouling layer and the regulation of the fouling layer habitat structure, rather than relying on strong acids, strong bases, or strong oxidizing agents.

[0046] S700. Determine if flux has recovered.

[0047] After completing the quorum suppression and gentle cleaning, the membrane system operating parameters are checked to determine whether the membrane flux has recovered to the set operating range. If the membrane flux has not recovered, the low-intensity acid-base pre-cleaning step is performed again, followed by another quorum suppression and gentle cleaning. When the membrane flux recovers to the set operating range, the process proceeds to the next step.

[0048] S800. Membrane performance recovery

[0049] Once the membrane flux recovers to the set operating range, it is determined that the membrane performance has been effectively restored, and the membrane system can re-enter a stable operating state.

[0050] S900. End of cleaning process.

[0051] Example 1

[0052] This embodiment provides a mild membrane fouling cleaning method based on swarm immunity suppression and habitat regulation, and gives its specific implementation process.

[0053] Reverse osmosis membrane modules that have experienced flux decline after long-term operation were selected as the cleaning targets. The cleaning process was initiated when the membrane flux dropped to 85% of the initial stable flux.

[0054] The cleaning process includes the following steps:

[0055] (1) Low-intensity acid pre-cleaning

[0056] An acidic cleaning solution was prepared using deionized water, and the pH of the cleaning solution was adjusted to 4.5. The solution was then circulated and cleaned for 30 minutes at 30°C at 0.8 times the normal operating flow rate of the system.

[0057] (2) Low-intensity alkaline pre-cleaning

[0058] After emptying the acidic cleaning solution, rinse the membrane module with deionized water, then prepare an alkaline cleaning solution, adjust the pH of the cleaning solution to 10.5, and circulate the cleaning solution for 30 minutes at 25°C.

[0059] (3) Gentle cleaning to suppress group infection

[0060] First, a cleaning agent for mild swarm suppression cleaning is prepared, wherein vanillin is selected as the swarm inhibitor. During preparation, vanillin is first dissolved in ethanol to form a homogeneous pre-solution. Then, the pre-solution and a buffer are added together to deionized water and mixed thoroughly to obtain the cleaning agent. The cleaning agent contains 0.05 wt% vanillin, 0.1 wt% buffer, 0.5 wt% ethanol as the co-solvent, and the remainder is deionized water. Subsequently, the cleaning agent is diluted with water to form a cleaning solution, ensuring the swarm inhibitor concentration in the cleaning solution is 50 mg / L. The temperature of the cleaning solution is controlled at 30°C to maintain the cleaning temperature at 30°C, and the membrane module is subjected to mild swarm suppression cleaning for 60 min using the same circulation method as the pre-cleaning process.

[0061] (4) Cleaning status judgment

[0062] After cleaning, the membrane module is rinsed with water and the system operating conditions are restored. The membrane flux recovery is then monitored. When the membrane flux recovers to the set operating range, the cleaning process ends and the cleaning efficiency is calculated.

[0063] Experimental results are as follows Figure 2 As shown, the cleaning efficiency of the membrane system after the first cleaning was 73.96%; after the second cleaning, the cleaning efficiency was 76.41%; and after the third cleaning, the cleaning efficiency was 74.88%.

[0064] The results show that, under multiple rounds of operation and cleaning conditions, the cleaning method described in this invention, which includes a gentle cleaning step to suppress swarming, can maintain a relatively stable cleaning efficiency during multiple cleaning processes, without showing a significant decrease with increasing cleaning frequency.

[0065] Example 2

[0066] This embodiment verifies a cleaning method that does not perform low-intensity acid-base pre-cleaning and directly performs swarm suppression mild cleaning under actual membrane fouling conditions, in order to evaluate the cleaning effect of the swarm suppression mild cleaning step under conditions without pre-acid-base cleaning.

[0067] Reverse osmosis membrane modules that experienced flux decline during operation were selected as the cleaning targets. The cleaning process was initiated when the membrane flux dropped to 85% of the initial stable flux. During the cleaning process, a low-intensity acidic or alkaline pre-cleaning step was not performed; instead, a mild cleaning solution containing swarm inhibitors was directly used to clean the membrane modules. All other cleaning conditions remained consistent with those in Example 1.

[0068] Under multiple rounds of operation and cleaning conditions, the changes in cleaning efficiency after each cleaning round were recorded. The experimental results show that, without performing low-intensity acid-base pre-cleaning, the swarm suppression mild cleaning can still effectively weaken and remove the membrane fouling layer, and the cleaning efficiency remains at a relatively stable level, but the overall cleaning efficiency is slightly lower than that of the cleaning method that includes low-intensity acid-base pre-cleaning in Example 1.

[0069] The results show that the swarm suppression mild cleaning step still has a certain cleaning ability without pre-cleaning with low-intensity acid and alkali, and the introduction of pre-cleaning with low-intensity acid and alkali helps to further improve the overall cleaning effect of the swarm suppression mild cleaning step.

[0070] Comparative Example 1

[0071] Comparative Example 1 used a traditional strong acid and strong alkali cleaning method to clean the reverse osmosis membrane module under the same operating conditions as in Example 1, and compared and verified the cleaning efficiency during multiple cleaning processes. This cleaning method does not include low-intensity acid and alkali pre-cleaning or swarm suppression gentle cleaning steps.

[0072] Experimental results are as follows Figure 2 As shown, the cleaning efficiency was 79.52% in the first cleaning process; it dropped to 62.63% in the second cleaning process; and further decreased to 53.17% in the third cleaning process.

[0073] The results show that when using traditional strong acid and strong alkali cleaning methods, the cleaning efficiency decreases significantly with the increase of cleaning cycles, indicating that the cleaning effect of this method gradually diminishes under multiple rounds of operation and cleaning.

[0074] The cleaning method of Example 1 and the cleaning method of Comparative Example 1 were tested as follows:

[0075] (1) Analysis of macroscopic morphological changes of the membrane surface before and after cleaning

[0076] The macroscopic morphological changes of the membrane surface contaminant layer before and after cleaning using the cleaning method of Example 1 and Comparative Example 1 of this invention were observed and analyzed, and the results are as follows: Figure 3 As shown.

[0077] in, Figure 3 (a) in Example 1 shows the membrane surface morphology before entering the swarm suppression and gentle cleaning step; Figure 3 (b) shows the membrane surface morphology after swarm suppression and gentle cleaning in Example 1. It can be observed that after swarm suppression and gentle cleaning, the fouling coverage on the membrane surface is significantly reduced, the continuity of the fouling layer is disrupted, and the membrane surface structure is clearer, indicating that the overall stability of the fouling layer is effectively weakened. Figure 3 (c) in Comparative Example 1 shows the macroscopic morphology of the fouling layer on the membrane surface before cleaning with strong acid and strong alkali. A clear continuous fouling layer can be observed on the membrane surface. Figure 3 (d) in Comparative Example 1 shows the surface morphology of the membrane after strong acid and strong alkali cleaning. Only a portion of the fouling layer was removed, and a significant amount of residual deposits remained on the membrane surface. This indicates that traditional strong acid and strong alkali cleaning alone is insufficient to effectively destroy the overall structure of the fouling layer.

[0078] (2) Microscopic morphology analysis of the membrane surface after cleaning

[0079] Electron microscopy was used to observe and analyze the microscopic morphological changes of the contaminant layer on the membrane surface after cleaning using the cleaning method of Example 1 and Comparative Example 1. The results are as follows: Figure 4 As shown.

[0080] in, Figure 4(a) shows the microstructure of the membrane surface after treatment with the swarm suppression and mild cleaning method in Example 1. It can be observed that after the swarm suppression and mild cleaning treatment, the structure of the fouling layer on the membrane surface is obviously loose and porous, the degree of binding between pollutants is significantly reduced, most of the fouling layer shows disintegration and peeling, and the degree of exposure of the membrane surface is significantly increased. Figure 4 (b) shows the microstructure of the membrane surface after treatment with the traditional strong acid and strong alkali cleaning method of Comparative Example 1. The electron microscopy results show that after the strong acid and strong alkali cleaning is completed, there is still a densely attached pollutant structure on the membrane surface. The overall continuity of the pollutant layer is relatively strong, indicating that the traditional strong acid and strong alkali cleaning method alone is difficult to effectively destroy the micro-stable structure of the pollutant layer.

[0081] (3) Changes in biomass on the membrane surface before and after cleaning

[0082] The changes in membrane surface biomass before and after cleaning using the methods of Example 1 and Comparative Example 1 were quantitatively measured. ATP content was used to characterize membrane surface biomass. The results are as follows: Figure 5 As shown, from Figure 5 The data shows that the ATP content on the membrane surface before washing was 15.23 ng / cm³. -2 After gentle washing to suppress quorum infection using the method described in Example 1, the ATP content on the membrane surface decreased to 8.25 ng / cm³. -2 After strong acid and strong alkali washing using the method of Comparative Example 1, the ATP content on the membrane surface was 13.84 ng / cm³. -2 It is evident that quorum suppression and gentle washing have a more significant effect on reducing biomass on the membrane surface.

[0083] (4) Content of inorganic contaminants on the membrane surface before and after cleaning

[0084] The content of inorganic contaminants on the membrane surface before and after cleaning using the cleaning methods of Example 1 and Comparative Example 1 was analyzed. Calcium and magnesium were selected as representative inorganic contaminants for determination. The results are as follows: Figure 6 As shown.

[0085] Before cleaning, the calcium content on the membrane surface was 42.36 μg cm⁻¹. -2 The magnesium content is 19.58 μg cm⁻¹ -2 After cleaning using the method of Example 1, the calcium content on the membrane surface was 26.91 μg / cm³. -2 The magnesium content is 11.63 μg cm⁻¹ -2 This indicates that the content of inorganic contaminants on the membrane surface was effectively reduced under mild cleaning conditions; after cleaning using the method of Comparative Example 1, the calcium content on the membrane surface decreased to 18.74 μg / cm³. -2 The magnesium content decreased to 7.92 μg cm. -2This indicates that traditional strong acid and strong alkali cleaning methods mainly remove inorganic pollutants such as calcium and magnesium by enhancing the dissolution process.

[0086] It should be noted that the method of this invention does not primarily rely on enhancing the dissolution of inorganic salts for cleaning. Instead, it weakens the overall stability of the fouling layer by regulating the structural state of microorganisms within the fouling layer, allowing inorganic contaminants to be removed as the fouling layer disintegrates and peels off. Therefore, while the amount of inorganic contaminants remaining on the membrane surface after a single cleaning is slightly higher than that of traditional strong acid and strong alkali cleaning methods, it is more beneficial for maintaining the operational stability of the membrane system under multiple operation and cleaning cycles.

[0087] (5) Actual engineering operation test

[0088] The mild membrane fouling cleaning method based on swarm immunity suppression and habitat regulation described in this invention was applied to the actual operation and maintenance of different membrane process sections in an industrial water treatment system of a coal chemical plant. The cleaning conditions and the effects of multiple cleaning cycles were statistically analyzed and compared. The membrane process sections involved included a single-stage reverse osmosis system, a double-stage reverse osmosis system, a single-stage nanofiltration system, and a double-stage nanofiltration system. The cleaning operation conditions for different membrane process sections are shown in Table 1. For the single-stage and double-stage reverse osmosis processes, the cleaning trigger condition was a drop in membrane flux to 80–85% of the initial stable flux. For the single-stage and double-stage nanofiltration processes, the cleaning trigger condition was a drop in membrane flux to 85–88% of the initial stable flux. Regarding cleaning operation parameters, the cleaning temperature for the reverse osmosis process was controlled within the range of 25–30℃, and the cleaning temperature for the nanofiltration process was controlled within the range of 30–35℃. The cleaning pressure for each membrane process section was controlled within the range of 0.2–0.3 MPa to ensure a stable circulating cleaning process. The single-round cleaning time for the reverse osmosis process section is 60–90 min, and the single-round cleaning time for the nanofiltration process section is 90–120 min.

[0089] Table 1 Cleaning operation conditions for different membrane process sections

[0090]

[0091] Under the above cleaning conditions, the cleaning effect of different membrane process sections was statistically analyzed in multiple rounds. The cleaning effect was calculated based on the recovery of membrane flux after cleaning. The relevant data are shown in Table 2.

[0092] Table 2. Group invasion suppression and mild cleaning effects of different membrane process stages

[0093]

[0094] The cleaning interval coefficient is a dimensionless parameter used to characterize the difference in the operating cycle of the membrane system under different cleaning methods. It is defined as the ratio of the average operating cycle corresponding to a certain cleaning method to the average operating cycle corresponding to the traditional strong acid and strong alkali cleaning method under the same cleaning triggering conditions. The cleaning interval coefficient of the traditional strong acid and strong alkali cleaning method is defined as 1.00, and the cleaning interval coefficients of other cleaning methods are normalized based on this.

[0095] For the membrane process section employing the mild cleaning method for suppressing group sensitivity of this invention, the cleaning efficiency of the first-stage reverse osmosis system after the first round of cleaning is 88.92%, the efficiency after the third round is 80.36%, and the efficiency after the fifth round is 75.14%, with a corresponding cleaning interval coefficient of 1.30. For the second-stage reverse osmosis system, the cleaning efficiencies after the first, third, and fifth rounds of cleaning are 89.47%, 81.28%, and 76.02%, respectively, with a cleaning interval coefficient of 1.32. For the first-stage nanofiltration system, the cleaning efficiency after the first round of cleaning is 90.15%, the efficiency after the third round is 82.41%, and the efficiency after the fifth round is 77.36%, with a cleaning interval coefficient of 1.28. For the second-stage nanofiltration system, the cleaning efficiencies after the first, third, and fifth rounds of cleaning are 87.68%, 79.52%, and 74.26%, respectively, with a cleaning interval coefficient of 1.29.

[0096] As a control, under the same membrane process section and the same cleaning triggering conditions, the membrane system was cleaned multiple times using the traditional strong acid and strong alkali cleaning method. The cleaning effect is shown in Table 3.

[0097] Table 3. Effects of traditional strong acid and strong alkali cleaning on different membrane process stages

[0098]

[0099] The first-stage reverse osmosis system achieved a cleaning efficiency of 78.36% after the first cleaning cycle, 65.24% after the third cycle, and 61.08% after the fifth cycle, with a cleaning interval coefficient of 1.00. The second-stage reverse osmosis system achieved cleaning efficiencies of 79.12%, 66.08%, and 62.14% after the first, third, and fifth cycles, respectively, with a cleaning interval coefficient of 1.00. The first-stage nanofiltration system achieved a cleaning efficiency of 80.04% after the first cleaning cycle, 67.21% after the third cycle, and 63.02% after the fifth cycle, with a cleaning interval coefficient of 1.00. The second-stage nanofiltration system achieved cleaning efficiencies of 77.58%, 64.36%, and 60.18% after the first, third, and fifth cycles, respectively, with a cleaning interval coefficient of 1.00 for all cycles.

[0100] Under continuous operation and multiple cleaning cycles, the reverse osmosis membrane system using the method of this invention maintained a cleaning efficiency of 74.26%–90.15% after five consecutive cleaning cycles, and did not show a significant decrease with increasing cleaning cycles. Using the same membrane flux reduction threshold as a comparison condition, the cleaning interval coefficient for each membrane process segment using the method of this invention was 1.28–1.32, indicating that the single operating cycle was extended under the same operating conditions.

[0101] Regarding the consumption of cleaning agents, the dosage of strong acid and strong alkali cleaning agents is reduced by approximately 35%–40% compared to traditional strong acid and strong alkali cleaning methods when using the method of this invention. Furthermore, considering operational factors such as cleaning agent consumption, cleaning frequency, system downtime, and manual maintenance, the overall cleaning and maintenance cost of the membrane system using the method of this invention is reduced by approximately 20%–30%.

[0102] Under the same membrane process section and the same flux reduction threshold, the traditional strong acid and strong alkali cleaning method has a shorter operating cycle, with a cleaning interval coefficient of 1.00. At the same time, the consumption of strong acid and strong alkali agents is high during the cleaning process, which increases the frequency of system shutdown and maintenance, resulting in higher operating and maintenance costs.

[0103] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0104] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A mild membrane fouling cleaning method based on swarm immunity suppression and habitat regulation, characterized in that, Includes the following steps: (1) During the operation of the membrane system, when membrane fouling causes the membrane system operating parameters to deviate from the set operating range, the cleaning process is initiated; (2) After starting the cleaning process, determine whether low-intensity acid and alkali pre-cleaning is required based on the current operating status of the membrane system; If it is determined that a low-intensity acid-base pre-cleaning is required, a low-intensity acid-base pre-cleaning is performed on the membrane. If it is determined that a low-intensity acid-base pre-cleaning is not necessary, proceed to the group infection suppression and gentle cleaning step. (3) When entering the quorum suppression mild cleaning step, a mild cleaning agent containing quorum inhibitor is applied to the membrane without introducing a strong oxidizing bactericide. By regulating the structure of the fouling layer and the microbial habitat conditions, and interfering with the transmission of microbial quorum sensing signals, the membrane is subjected to quorum suppression mild cleaning. (4) After completing the swarm suppression mild cleaning, the cleaning status is determined based on the membrane system operating parameters. If the membrane flux has not recovered to the set operating range, the low-intensity acid and alkali pre-cleaning is performed and the swarm suppression mild cleaning is performed in sequence. Once the membrane system operating parameters return to the set operating range, the cleaning process ends.

2. The mild membrane fouling cleaning method according to claim 1, characterized in that, The low-intensity acid-base pre-cleaning includes low-intensity acid pre-cleaning and low-intensity alkaline pre-cleaning, wherein the pH of the cleaning solution for the low-intensity acid pre-cleaning is 3.5 to 6.5, and the pH of the cleaning solution for the low-intensity alkaline pre-cleaning is 9.0 to 11.

5.

3. The mild membrane fouling cleaning method according to claim 2, characterized in that, During the low-intensity acid-base pre-cleaning and swarm-inhibiting mild cleaning processes, the cleaning temperature does not exceed 40°C.

4. The mild membrane fouling cleaning method according to claim 1, characterized in that, The cleaning agent used for the mild cleaning of the swarm suppression comprises, by weight percentage, 0.001% to 1.0% swarm suppressant, 0.05% to 1.0% buffer, 0% to 5.0% alcohol co-solvent, and the balance being deionized water, wherein the swarm suppressant is a non-in vivo chemical substance.

5. The mild membrane fouling cleaning method according to claim 4, characterized in that, The swarm inhibitor is selected from one or more of lactones, esters, aromatic aldehydes, aromatic phenols, indoles, polyphenols, flavonoids, or their derivatives.

6. The mild membrane fouling cleaning method according to claim 5, characterized in that, The swarm inhibitors include one or more of the following: γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, aliphatic lactone derivatives, thymol, eugenol, isoeugenol, vanillin, cinnamaldehyde, carvacrol, green tea polyphenols, epigallocatechin gallate, curcumin, indole, or derivatives thereof.

7. The mild membrane fouling cleaning method according to claim 4, characterized in that, The cleaning agent does not contain strong oxidizing bactericides.

8. The mild membrane fouling cleaning method according to any one of claims 4 to 7, characterized in that, In the preparation of the cleaning agent, the susceptibility inhibitor is first dissolved in an alcohol-based co-solvent to form a homogeneous pre-solution. Then, the pre-solution and the buffer are added together to deionized water and mixed evenly to obtain the cleaning agent.

9. The mild membrane fouling cleaning method according to claim 8, characterized in that, The cleaning agent is diluted with water to form a cleaning solution, which is then used to perform swarm suppression and gentle cleaning of the membrane.

10. The mild membrane fouling cleaning method according to claim 9, characterized in that, The mass concentration of the quorum inhibitor in the cleaning solution is from 10 mg / L to 100 mg / L.

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