Membrane Chemical Cleaning Research Articles

Adsorptive chito-beads for control of membrane fouling

Chitosan has excellent antimicrobial, adsorption, heavy metal removal, and adhesion properties, making it a good substitute for microplastic-based cleaners. Here, chitosan microbeads (chito-beads) of various sizes ranging from 32 μm to 283 μm were prepared via emulsion using a liquid on oil method and the feasibility of using them as an essential constituent in a chemical cleaning solution for a reverse-osmosis (RO) membrane-fouling-control process was assessed. Prior to the assessment the cleaning efficiency of a solution containing chito-beads, the interaction energy between chitosan and a representative organic foulant (humic acid (HA)) in a RO membrane fouling was analyzed using colloidal atomic force microscopy, and the strongest attraction between chitosan and HA was observed in an aqueous solution. When comparing the membrane cleaning efficiency of cleaning solutions with and without chito-beads, smaller chito-beads (32 μm and 70 μm) were found to have higher cleaning efficiency. Applications of chito-beads to the membrane cleaning process can enhance the cleaning efficiency through the physicochemical interaction with organic foulants. This study can widen the use of chito-beads as an additive to membrane chemical cleaning solutions to control membrane fouling in other membrane processes as well.

Effective and low-toxicity: A membrane cleaning method using peroxymonosulfate catalytic chlorination

In chemical membrane cleaning, the challenge is to efficiently remove irreversible fouling while minimizing the impact on membrane materials. Particularly, traditional hypochlorite cleaning will further lead to the generation of toxic halogenated by-products. To address these issues, a combined system composed of peroxymonosulfate and chloride (PMS/Cl−) was applied to clean irreversible-humic-acid-fouled polyethersulfone (PES) membranes. After fouled membranes were soaked for 1 h in a PMS/Cl− solution (10 mM/15 mM) at 25 °C under neutral conditions, 94% flux recovery and 96% resistance removal were realized. Surface properties of virgin and cleaned membranes were very similar, confirming the effectiveness of the PMS/Cl− solution in removing irreversible foulants. The stability of membrane separation performance during multiple fouling and cleaning cycles further confirmed the minimal impact on membrane materials. Rapid diminution of the peaks centered in the region of fulvic-like and humic-like components, monitored under 3D-fluorescence for the cleaning solution, was attributed to PMS-catalyzed chlorination, thereby revealing the primary foulant detachment mechanism. Crucially, the approach exhibited lower toxicity than hypochlorite, as evidenced by reduced halogenated by-products and lower acute toxicity to Photobacterium phosphoreum T3. Overall, this novel cleaning system is promising for the efficient and environmentally friendly removal of irreversible organic foulants in practical water-treatment.

Emerging algal organic matter from simulated on-line chemical cleaning of ultrafiltration membranes treating algae-containing water

Massive reproduction of algae due to the eutrophication of water body poses a new challenge to the water ecosystem. Despite ultrafiltration (UF) acting as an effective method to treat algae-containing waters, on-line chemical cleaning is frequently utilized to sustain the permeability of UF membranes. However, little attention is currently paid on the side-effects of practical on-line chemical cleaning on aqueous environments. Therefore, this work evaluated the generation of algae organic matter triggered by diverse membrane cleaning reagents (i.e., HCl, NaOH, NaClO, SDS and CA), and their subsequent fate in terms of biodegradation and membrane retention. The results indicated that NaOH, HCl and NaClO caused serious damage and lysis of algal cells, leading to the significant release of dissolved organic matter (DOM), while CA and SDS induced negligible DOM release. The occurrence of DOM release was able to cause extra biofouling, thus deteriorating the UF permeability. Furthermore, DOM was characterized in terms of three molecular weight ranges, i.e., high molecular weight (HMW, > 3400 Da), medium molecular weight (MMW, 150–3400 Da), and low molecular weight (LMW, <150 Da). Protein-related substances in the range of HMW and MMW were primarily produced under HCl and NaOH exposures. In contrast, NaClO led to an obvious release of humic-like materials with MMW. During the next round of UF operation, roughly 17 % to 31 % of these released DOM could be removed by via the joint actions of suspended algae biodegradation and fouling layer retention. Nevertheless, roughly 69 % to 83 % of these produced DOM eventually entered into the UF permeate, resulting in the deterioration of permeate quality. Consequently, the detailed mechanisms of DOM generation and subsequent removal by UF were proposed, which re-examined the origins of emerging contaminants in aqueous environment and shed new light on the strategies to ameliorate current practice of on-line membrane chemical cleaning.

Insights into Co3O4 nano-rod/peroxymonosulfate catalytic oxidation system for chemical cleaning ultrafiltration membrane: Performance, mechanisms, and effects on the membrane stability

In this study, Co3O4 nano-rod (Co3O4-NR) with (110) crystal plane predominant exposure is prepared by a hydrothermal method, and peroxymonosulfate (PMS) was activated via them for ultrafiltration membrane (PVDF and PES membrane) cleaning. Co3O4-NR with (110) planes exposed obtained abundant oxygen vacancies (OV) and low oxidation state Co (Co2+) and therefore showed excellent ability for PMS activation. The Co3O4-NR/PMS system did not require long-term immersion in a high-concentration chemical reagent solution compared with conventional ultrafiltration membrane chemical cleaning. The cleaning process, which was conducted for only 15 min in Co3O4-NR (1.6 g/L)/PMS (2 mM) solution, was sufficient to restore almost all the permeate flux and could remove essentially all the irreversible foulants. The excellent membrane cleaning performance of the Co3O4-NR/PMS system was attributed to the generation of 1O2 and O2•−, which degraded the large-molecule, hydrophobic natural organic matter (NOM) into small-molecule, hydrophilic organic matter. Cyclic experiments showed that Co3O4-NR had excellent reusability, which offered significant cost savings. The consecutive chemical cleaning experiments indicated that the Co3O4-NR/PMS maintained the membrane stability better than the traditional chlorine cleaning method. The system effectively averts membrane damage and polymer structure changes caused by long-term exposure to oxidants. In conclusion, the Co3O4-NR/PMS system has significant advantages in membrane cleaning and broad application prospects.

Fouling of reverse osmosis membrane: Autopsy results from a wastewater treatment facility at central park, Sydney

Membrane fouling is an inevitable phenomenon and common issue in Reverse Osmosis (RO) membrane systems used for water reclamation. Severe membrane fouling in RO system could consequently increases the operation cost as it requires frequent membrane chemical cleaning process thus consuming more chemical agents and shorten lifespan of RO membrane module. In this study, potential foulants of RO membranes that are used at Sydney's urban wastewater recycling facility which treated for domestic and commercial wastewaters, were investigated via membrane autopsy method. The three-year-old spiral wound RO membrane modules were taken from the site for membrane autopsy and to investigate major fouling factors as well as in-depth study of fouling mechanisms throughout various characterization methods. Additionally, a flux recovery rate of fouled RO membranes via the chemical cleaning was also examined using different kind of chemical cleaning agents to find a most effective chemical cleaning combination.

Grace licenses UNIPOL PP process technology to GAIL (India) Ltd

The productivity of membrane process in any application is governed by rate of fouling deposition and membrane cleaning effectiveness. Chemical membrane-cleaning has demonstrated considerable restoration of membrane flux, but their repetitive use causes detrimental effects on membrane structure and properties thereby resulting in premature ageing and reduced lifespan of membranes. The objective of this study was to determine the long-term impact of conventional cleaning chemicals such as sodium hydroxide (NaOH), sodium hypochlorite (NaOCl) and hydrochloric acid (HCl) on physical and chemical properties of tubular polyvinylidene fluoride (PVDF) membrane. The membrane samples were soaked in individual chemicals for a total duration of 720 h and the results indicated that each chemical had different extent of ageing effects on membrane conformation and chemistry

Tosoh reports consolidated results for 1Q FY 2022: Speciality Group

The productivity of membrane process in any application is governed by rate of fouling deposition and membrane cleaning effectiveness. Chemical membrane-cleaning has demonstrated considerable restoration of membrane flux, but their repetitive use causes detrimental effects on membrane structure and properties thereby resulting in premature ageing and reduced lifespan of membranes. The objective of this study was to determine the long-term impact of conventional cleaning chemicals such as sodium hydroxide (NaOH), sodium hypochlorite (NaOCl) and hydrochloric acid (HCl) on physical and chemical properties of tubular polyvinylidene fluoride (PVDF) membrane. The membrane samples were soaked in individual chemicals for a total duration of 720 h and the results indicated that each chemical had different extent of ageing effects on membrane conformation and chemistry

Clariant expands in China by a joint-venture production facility for high-end stabilizer additives

The productivity of membrane process in any application is governed by rate of fouling deposition and membrane cleaning effectiveness. Chemical membrane-cleaning has demonstrated considerable restoration of membrane flux, but their repetitive use causes detrimental effects on membrane structure and properties thereby resulting in premature ageing and reduced lifespan of membranes. The objective of this study was to determine the long-term impact of conventional cleaning chemicals such as sodium hydroxide (NaOH), sodium hypochlorite (NaOCl) and hydrochloric acid (HCl) on physical and chemical properties of tubular polyvinylidene fluoride (PVDF) membrane. The membrane samples were soaked in individual chemicals for a total duration of 720 h and the results indicated that each chemical had different extent of ageing effects on membrane conformation and chemistry

Validation and application of a membrane filtration evaluation protocol for oil-water separation

Membrane filtration processes like microfiltration (MF) and ultrafiltration (UF) are proven to be effective in industrial wastewater treatment, including oil-water separation, as they generate suitable quality permeate for water reuse applications. Various research efforts have been conducted in areas of developing and/or modifying commercial MF/UF membrane materials through synthesizing new advanced polymers that promise improvement in oil-water separation performance. Although multiple MF/UF testing procedures were developed, there is still a gap in literature on having a comprehensive protocol that assesses the performance of the membranes in terms of flux, rejection, fouling, and cleanability. This paper delivers a robust bench scale testing procedure incorporating experiences and lessons learned from literature. The evaluation procedure includes three main testing steps: initial characterization, operating performance, and cleaning and recovery. The protocol was designed to mimic industrial conditions by using a representative synthetic produced water solution and operating multiple consecutives cycles of oil-water filtration followed by membrane chemical cleaning. The procedure was initially validated on multiple commercial MF/UF membranes having different pore sizes/MWCOs and chemistries obtained from various manufacturers and then applied to evaluate emerging membrane materials. The protocol was found to be reliable in evaluating the performance trends of various commercial membranes and effective in comparing the performance of emerging membranes. The developed procedure is proposed to be applied by researchers to assess the performance of new membrane materials as compared to relevant commercial products.

Recent development of photocatalytic nanomaterials in mixed matrix membrane for emerging pollutants and fouling control, membrane cleaning process

Membrane-based separation is an area of extensive research in wastewater treatment, which includes the control of pollution and reuse of water. The fabrication and modification membranes for prevention and reduction of pollution to provide quality water with fouling-free membranes through the wastewater treatment are the progressive approaches in the industries. Several research works have been extensively working on modification and fabrication polymer membranes with integration of advanced oxidation process (AOP) to overcome the membrane fouling. This review describes the modification of membranes with various nanomaterials such as inorganic and modified carbon which can be used for pollution control and enhance the anti-fouling properties of ultrafiltration membranes. The effects on nanomaterials loading percentage, nanomaterials interaction with the polymers and rejection performances of the surface tuned membrane are elaborated. Secondly, the fouled membrane chemical cleaning process and NaOCl adverse effect on polymer structure are critically investigated. Moreover, state-of-art in the photocatalytic self-cleaning process are reviewed in this manuscript, and future perspectives on fouling mitigation based on AOP integrated membrane technology have also discussed.

Dead-end ultrafiltration of rich glucosinolates juice extracted from mustard defatted meal: Effects of operating conditions on permeate quality and membrane fouling

Glucosinolates (GSL) (β-thioglucoside-N-hydroxysulfates) are rich-sulfur secondary metabolites with high reactive biological properties interesting for biofumigation. Brown mustard (Brassica juncea) seeds are rich in GSL mainly in sinigrin (≈100 μmol/g DM) and gluconapin (≈12 μmol/g DM). GSL should be extracted in their native form and then purified to be used as natural biopesticide. In this work, dead-end ultrafiltration of a rich glucosinolates juice expressed from defatted seed meal was studied and optimized by tuning experimental conditions. The impact of membrane MWCO (5–150 kDa), operating pressure (1–5 bar) and stirring (0–600 rpm) on the filtration kinetic and the permeate quality were studied. In the optimal conditions, most of impurities (proteins, colloids) were removed and the juice purity was increased from 35.2% to 90.1% without degrading the GSL. Modeling showed that the fouling mechanism is strongly depending on the applied stirring velocity. More importantly, fouling has been efficiently removed after membrane chemical cleaning using NaOH solution for membrane regeneration. The purified permeate rich in glucosinolates is very suitable for biopesticides formulation and the retentate concentrated in proteins may be valorized as animal feeding.

Impact of cleaning agents on properties of tubular polyvinylidene fluoride (PVDF) membrane

The productivity of membrane process in any application is governed by rate of fouling deposition and membrane cleaning effectiveness. Chemical membrane-cleaning has demonstrated considerable restoration of membrane flux, but their repetitive use causes detrimental effects on membrane structure and properties thereby resulting in premature ageing and reduced lifespan of membranes. The objective of this study was to determine the long-term impact of conventional cleaning chemicals such as sodium hydroxide (NaOH), sodium hypochlorite (NaOCl) and hydrochloric acid (HCl) on physical and chemical properties of tubular polyvinylidene fluoride (PVDF) membrane. The membrane samples were soaked in individual chemicals for a total duration of 720 h and the results indicated that each chemical had different extent of ageing effects on membrane conformation and chemistry

Performance of a membrane bioreactor and a moving bed biofilm reactor–membrane bioreactor treating table olive processing wastewater: a comparative study

AbstractBACKGROUNDTwo laboratory‐scale experimental systems – a membrane bioreactor (MBR) and a moving bed biofilm reactor–membrane bioreactor (MBBR‐MBR), both treating real high‐strength, saline wastewater from a table olive processing plant – were operated under identical conditions to comparatively evaluate their performance for three different hydraulic retention times (HRTs) of 88, 96 and 104 h.RESULTSThe biological process of both systems, after appropriate biomass acclimatization, was stable and the removal efficiencies were rather high; i.e., regarding total organic carbon (TOC) ≥86.4% and ≥85.6% for the MBR and MBBR‐MBR, respectively, and ≥89.1% regarding total polyphenols (TPh) for both systems. Concerning TOC and TPh removal, no statistically significant difference (p &lt; 0.05) was observed between the two systems. Reduction of HRT resulted in a slight decrease in mean TOC removal efficiency, but the mean TPh removal was practically unchanged. No membrane chemical cleaning was applied to either system during the 85‐day long continuous operation.CONCLUSIONThe comparative assessment showed that both systems (i.e., MBR and MBBR‐MBR) are effective for the advanced biological treatment of table olive processing wastewater and can achieve quite high removal efficiencies of organic matter and TPh. However, direct effluent reuse for irrigation purposes seems to be hindered by its high salinity. No significant differences were observed in the performance of these systems, apart from the increased aeration (and related energy costs), which is necessary to keep the biofilm carriers floating in the case of the MBBR‐MBR. © 2020 Society of Chemical Industry

Performance evaluation of conventional membrane bioreactor and moving bed membrane bioreactor for synthetic textile wastewater treatment

In this study, conventional membrane bioreactor (MBR) and moving bed-membrane bioreactor (MB-MBR) processes were compared in synthetic textile wastewater treatment. For this purpose, the bioreactors were operated as a conventional MBR, an MB-MBR with a biocarrier filling ratio of 20 % and an MB-MBR with a biocarrier filling ratio of 10 %, respectively. In the conventional MBR operation, 93.1 % chemical oxygen demand (COD) and 87.1 % color (Reactive Red 390) removal efficiencies were obtained. In both MB-MBR operations, almost equal COD and color removal efficiencies were found as 98.5 % and 89.5 %, respectively. Moreover, offline physical and chemical membrane cleaning processes were applied every other day and every 15 days throughout the conventional MBR operation, respectively, while no physical or chemical membrane cleaning was required during both MB-MBR operations. Furthermore, lower polysaccharide concentrations of extracellular polymeric substances (EPS) and floc sizes of sludge and higher zeta potential of sludge were determined in MB-MBR. Considering the obtained results, it may be stated that the MB-MBR process is an attractive treatment technology for reducing membrane fouling propensity for treatment of textile wastewater.

Membrane cleaning of ultrafiltration in the combined membrane filtration processes and health risk assessment

This study focused on ultrafiltration membrane fouling mitigation and potential secondary pollution induced by membrane chemical cleaning. Based on the single factor experiment, the chemically enhanced backwash (CEB)11chemically enhanced backwash (CEB). operating parameters were optimized by response surface methodology in three combined membrane filtration processes, i.e., coagulation/ultrafiltration (Al/UF),22coagulation/ultrafiltration (Al/UF). adsorption/ultrafiltration (PAC/UF)33adsorption/ultrafiltration (PAC/UF). and oxidation/ultrafiltration (Ozone/UF).44oxidation/ultrafiltration (Ozone/UF). Then the optimal control models of CEB membrane cleaning technologies were established, which indicated high credibility and accuracy. According to the quadratic response surface model, the optimum cleaning parameters including backwash duration (BD),55backwash duration (BD). reagent concentration (RC),66reagent concentration (RC). backwash interval (BI)77backwash interval (BI). and backwash flux (BF)88backwash flux (BF). of Al/UF, PAC/UF and Ozone/UF were 4 min, 29 mg L−1, 60 min, 23 L (m2 h)−1; 6 min, 69 mg L−1, 60 min, 40 L (m2 h) −1; 2.5 min, 40 mg L−1, 93 min, 15 L (m2 h)−1. Health risk assessment of the effluent quality showed that the CEB byproducts from the combined Al/UF and PAC/UF process did not pose carcinogenic or non-carcinogenic health risks. Although the CEB byproducts from Ozone/UF were not a non-carcinogenic health risk, some carcinogenic risk is still evident. In order to ensure the safety and quality of drinking water, adjusting the operating parameters or adding other processes is needed to reduce the concentration of byproducts in the effluent.

Ultrafiltration and microfiltration membrane performance, cleaning, and flux recovery for microalgal harvesting

Membrane material, pore size, and cleaning strategy are important factors for microalgal membrane harvesting. In this study, harvesting of Scenedesmus acuminatus cultivated in pilot scale using nine ultrafiltration and three microfiltration membranes was carried out in cross-flow filtration system to compare their filtration performance and flux recovery after physical and chemical cleaning. The 0.45-μm PVDF-AsahiKASEI membrane had the highest average flux of 513.6 L m−2 h−1 among 12 membranes and 50-kDa PVC-Litree membrane had the highest average flux of 98.0 L m−2 h−1 among nine ultrafiltration membranes for 60 L S. acuminatus suspension harvesting. There were significantly positive correlations between membrane pore size, pure water flux, and average flux for S. acuminatus suspension harvesting. Generally, ultrafiltration membrane had moderate total fouling index (TFI) and high proportion of hydraulic reversible fouling index (HRFI) of more than 95%. The 0.45-μm PVDF-AsahiKASEI membrane had a low TFI but the lowest proportion of HRFI, associated with the residual microalgal cells, debris, and colloids on the inner surface and top ends of some cells inserted to big membrane pores, demonstrated by SEM image and reduced porosity from 65.9 to 60.2%. Compared to soaking cleaning, circulation cleaning strategy had a better flux recovery efficiency for 0.45-μm PVDF-AsahiKASEI membrane, proving that it would be a potential way in membrane chemical cleaning. This study demonstrated that microfiltration with high flux has great potential in microalgal harvesting if flux recovery efficiency can be significantly increased using suitable cleaning strategy such as circulation cleaning strategy.

A comparison between chemical cleaning efficiency in lab-scale and full-scale reverse osmosis membranes: Role of extracellular polymeric substances (EPS)

Chemical cleaning is vital for the optimal operation of membrane systems. Membrane chemical cleaning protocols are often developed in the laboratory flow cells (e.g., Membrane Fouling Simulator (MFS)) using synthetic feed water (nutrient excess) and short experimental time of typically days. However, full-scale Reverse Osmosis (RO) membranes are usually fed with nutrient limited feed water (due to extensive pre-treatment) and operated for a long-time of typically years. These operational differences lead to significant differences in the efficiency of chemical Cleaning-In-Place (CIP) carried out on laboratory-scale and on full-scale RO systems. Therefore, we investigated the suitability of lab-scale CIP results for full-scale applications. A lab-scale flow cell (i.e., MFSs) and two full-scale RO modules were analysed to compare CIP efficiency in terms of water flux recovery and biofouling properties (biomass content, Extracellular Polymeric Substances (EPS) composition and EPS adherence) under typical lab-scale and full-scale conditions. We observed a significant difference between the CIP efficiency in lab-scale (~50%) and full-scale (9–20%) RO membranes. Typical biomass analysis such as Total Organic Carbon (TOC) and Adenosine triphosphate (ATP) measurements did not indicate any correlation to the observed trend in the CIP efficiency in the lab-scale and full-scale RO membranes. However, the biofilms formed in the lab-scale contains different EPS than the biofilms in the full-scale RO modules. The biofilms in the lab-scale MFS have polysaccharide-rich EPS (Protein/Polysaccharide ratio = 0.5) as opposed to biofilm developed in full-scale modules which contain protein-rich EPS (Protein/Polysaccharide ratio = 2.2). Moreover, EPS analysis indicates the EPS extracted from full-scale biofilms have a higher affinity and rigidity to the membrane surface compared to EPS from lab-scale biofilm. Thus, we propose that CIP protocols should be optimized in long-term experiments using the realistic feed water.

In Situ Electrochemical Generation of Reactive Chlorine Species for Efficient Ultrafiltration Membrane Self-Cleaning.

Reactive membranes based on hydroxyl radical generation are hindered by the need for chemical dosing and complicated module and material design. Herein, we utilize an electrochemical approach featuring in situ generation of reactive (radical) chlorine species (RCS) through anodization of chloride ions for membrane self-cleaning. A hybridized carbon nanotube (CNT)-functionalized ceramic membrane (h-CNT/CM), possessing high hydrophilicity, permeability, and conductivity, was fabricated. Using carbamazepine (CBZ) as a probe, we confirmed the presence of RCS in the electrified h-CNT/CM. The rapid and complete degradation of CBZ in a single-pass ultrafiltration indicates a high localized RCS concentration within the three-dimensional porous CNT interwoven layer. We further demonstrate that the electrogeneration of RCS is a critical prestep for free chlorine (HClO and ClO-) formation. The self-cleaning efficiency of the membrane after fouling with a model organic foulant (alginate) was assessed using an electrified cross-flow membrane filtration system. The fouled h-CNT/CM exhibits a near complete water flux recovery following a short (1 min) self-cleaning with an applied voltage of 3 or 4 V and feed solutions of 100 or 10 mM sodium chloride, respectively. Considering the superior performance of the RCS-mediated self-cleaning compared to conventional membrane chemical cleaning using sodium hypochlorite, our results exemplify an effective strategy for in situ electrogeneration of RCS to achieve a highly efficient membrane self-cleaning.

Anaerobic hybrid membrane bioreactor for treatment of synthetic leachate: Impact of organic loading rate and sludge fractions on membrane fouling

In the present study, the treatment of synthetic landfill leachate was carried out using a lab-scale anaerobic hybrid membrane bioreactor (An-HMBR). The reactor was operated for 250 days at two days of hydraulic retention time (HRT). Average chemical oxygen demand (COD) removal efficiency was ≥ 88% at steady-state conditions at 100% raw leachate. As organic loading rate (OLR) increased from 1.6 to 13.9 Kg COD m−3 d−1, flux gradually declined from 70 to 52 L/m2 h (LMH) within 250 days. Chemical membrane cleaning enhanced the flux up to 75% of the initial flux at the final stage of the reactor. Reversible fouling (>90%) dominated over irreversible fouling (<8%). Membrane fouling was mainly caused by extracellular polymeric substances (EPS) fraction, which resulted in cake layer formation on the ceramic membrane used in the An-HMBR system. Membrane resistance increased with variables in the following order OLR > MLSS (mixed liquor suspended solids) > EPS > SMP (soluble microbial products). A nonlinear regression model developed for prediction of membrane resistance at different OLR can predict with an error of ±7%.

Stimulatory effects on bacteria induced by chemical cleaning cause severe biofouling of membranes

Abstract Chemical cleaning with hypochlorite is routinely used in membrane-based processes. However, a high-transient cleaning efficiency does not guarantee a low biofouling rate when filtration is restarted, with the physiological mechanisms largely remaining unknown. Herein, we investigated the microbial regrowth and surface colonization on membrane surfaces after NaOCl cleaning had been completed. Results of this study showed that the regrowth of model bacteria, Pseudomonas aeruginosa, was initially subject to inhibition due to the damage of key enzymes' activity and the accumulation of intracellular reactive oxygen species although the oxidative stress induced by NaOCl had been removed. However, with the resuscitation ongoing, the stimulatory effects became obvious, which was associated with the enhanced production of N-acyl homoserine lactones and the secretion of eDNA that ultimately led to more severe biofouling on the membrane surface. This study elucidates the inhibition–stimulation mechanisms involved in biofilm reformation (membrane biofouling) after membrane chemical cleaning, which is of particular significance to the improvement of cleaning efficiency and application of membrane technologies.