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Bioelectrochemical systems (BESs) are integrated water treatment technologies that generate electricity using organic matter in wastewater. In situ use of bioelectricity can direct the migration of ionic substances in a BES, thereby enabling water desalination, resource recovery, and valuable substance production. Recently, much attention has been placed on the microbial desalination cells in BESs to drive water desalination, and various configurations have optimized electricity generation and desalination performance and also coupled hydrogen production, heavy metal reduction, and other reactions. In addition, directional transport of other types of charged ions can remediate polluted groundwater, recover nutrient, and produce valuable substances. To better promote the practical application, the use of BESs as directional drivers of ionic substances requires further optimization to improve energy use efficiency and treatment efficacy. This article reviews existing researches on BES-driven directional ion transport to treat wastewater and identifies a few key factors involved in efficiency optimization. [ABSTRACT FROM AUTHOR]

The application of in situ electrochemical generation of ferrous (Fe(II)) ions for phosphorus (P) removal in wastewater treatment was investigated with attention to the efficacy, kinetics and mechanism. At concentrations typical of municipal wastewater, P could be removed by in situ Fe(II) with removal efficiency higher than achieved on addition of FeSO 4 and close to that of FeCl 3 under both anoxic and oxic conditions. The generation of alkalinity due to water electrolysis at the cathode created much higher pH conditions compared to FeSO 4 dosing thereby resulting in very different pathways of Fe solid phase formation and associated P removal mechanisms. The remarkably similar dependence of P removal on accumulated Fe for all investigated currents, initial P concentrations and DO conditions indicated that kinetic aspects did not play a role in P removal during in situ Fe(II) dosing. Thermodynamic modelling was undertaken to investigate possible solid phase formation pathways under anoxic conditions and these insights were extended to oxic conditions. The exclusive formation of ferrous hydroxide during anoxic in situ Fe(II) dosing implied that P removal occurred via coprecipitation and adsorption. Under oxic conditions, the high pH conditions would have resulted in rapid Fe(II) oxidation and formation of ferric oxyhydroxides with associated coprecipitation and adsorption effecting P removal in a similar pattern to that observed under anoxic conditions. In situ Fe(II) dosing represents a versatile option for chemical P removal with the precise control of Fe dosage to optimize FeP forms for possible P recovery. [ABSTRACT FROM AUTHOR]

Wastewater treatment plants are thought to be potential reservoirs of antibiotic resistance genes. In this study, GeoChip was used for analyzing multiple antibiotic resistance genes, including four multidrug efflux system gene groups and three β-lactamase genes in ten large-scale membrane bioreactors (MBRs) for municipal wastewater treatment. Results revealed that the diversity of antibiotic genes varied a lot among MBRs, but about 40% common antibiotic resistance genes were existent. The average signal intensity of each antibiotic resistance group was similar among MBRs, nevertheless the total abundance of each group varied remarkably and the dominant resistance gene groups were different in individual MBR. The antibiotic resistance genes majorly derived from Proteobacteria and Actinobacteria. Further study indicated that TN, TP and COD of influent, temperature and conductivity of mixed liquor were significant ( P < 0.05) correlated to the multiple antibiotic resistance genes distribution in MBRs. [ABSTRACT FROM AUTHOR]

Microbial desalination cells are considered a low-energy-consumption, clean technology to simultaneously purify wastewater and desalinate saline water by utilizing the in situ energy source contained in wastewater. To enhance desalination performance and achieve an optimal membrane stack configuration, an enlarged stacked microbial desalination cell (SMDC) has been developed and tested with 6–14 desalination cells. The cross-membrane area of the enlarged SMDC is 100 cm 2 . The anode and cathode volumes are both 200 mL. To reduce internal resistance, the width of desalination cells is kept as <0.5 mm. The optimal configuration with 10 desalination cells achieves the highest total desalination rate (TDR) of 423 mg/h and the highest charge transfer efficiency (CTE) of 836% when treating the 20 g/L NaCl solution. During this process, the junction potential across membranes increases from 0 to 374 mV, and occupies up to 74% of the total potential loss inside the SMDC. This shows that the SMDC used in this work achieves the highest TDR and CTE among the reported studies, and the junction potential should be effectively controlled to achieve the desired desalination performance in future practical applications. [ABSTRACT FROM AUTHOR]

A homogeneous carbon membrane with multi-functions of microfiltration, electron conduction, and oxygen reduction catalysis was fabricated without using noble metals. The produced carbon membrane has a pore size of 553 nm, a resistance of 6.0 ± 0.4 Ω cm 2 /cm, and a specific surface area of 32.2 m 2 /g. After it was assembled in microbial fuel cell (MFC) as filtration air cathode, a power density of 581.5 mW/m 2 and a current density of 1671.4 mA/m 2 were achieved, comparable with previous Pt air cathode MFCs. The filtration MFC was continuously operated for 20 days and excellent wastewater treatment performance was also achieved with removal efficiencies of TOC (93.6%), NH 4 + –N (97.2%), and total nitrogen (91.6%). In addition, the carbon membrane was much cheaper than traditional microfiltration membrane, suggesting a promising multi-functional material in wastewater treatment field. [ABSTRACT FROM AUTHOR]

Abstract: Iron injection through electrolytically mediated oxidative dissolution of an iron electrode has been proposed as a convenient means of inducing coagulation of wastewater contaminants and thereby reducing the extent of membrane fouling in membrane bioreactors (MBRs). In order to investigate the effect of electrically released iron on membrane fouling propensity, alginate was selected as a model soluble microbial product, and the impact of electrolyzed iron on the specific resistance to filtration (SRF) quantified for a range of electrolysis times. It was confirmed that ferrous iron (Fe(II)) was initially released with concentration increasing proportionally with time of application of electric current in agreement with Faraday's Law. The fouling propensity of alginate increased at early loading times due to the formation of alginate gels and highly stabilized colloidal species. The presence of calcium ions was found to exacerbate this gelation process as a result of i) alginate bridging by Ca2+ ions, and ii) the reduced capacity of the alginate to bind iron and stabilize iron oxide particles. Significant reduction in fouling propensity was observed at higher iron loadings as a result of the formation of substantive amounts of iron oxides which, most likely, adsorbed alginate and prevented gel formation. [Copyright &y& Elsevier]

• The system performs best at 6 h hydraulic retention time. • It achieved 0.215 g/h salts removal at a wastewater treatment capacity of 10 L/d. • Microbial community structures are consistent with the spatial structure of cathode. • Catholyte circulation should be effective for the stratified microbial structures. In this study, two dual-anode assembled microbial desalination cells (DA-MDCs) composed of two anodes, one cathode and two membrane stacks were constructed, with a hollow fiber membrane (HFM) module coupling into the cathode to filtrate suspended solids and microbes. Enriched domestic wastewater treatment performance of the DA-MDC system under different hydraulic retention time (HRT) was investigated in detail. When HRT sequentially decreased from 10 h, 8 h, 6 h to 4 h, the conductivity in diluent effluent kept stable at first, but increased 519% at 4 h compared with 6 h. Nevertheless, the chemical oxygen demand, total nitrogen and total phosphorus in the effluent met the wastewater discharge standards in China at all HRTs. Additionally, transmembrane pressure of the HFM modules increased sharply when HRT changed from 6 h to 4 h. Therefore, HRT 6 h was selected as the optimal condition. Under such short HRT, the system realized wastewater treatment capacity of 10 L/d, surpassing all bio-cathode microbial desalination cell systems aiming to realize efficient treatment of domestic wastewater. Additionally, the salt removal rate of 0.215 g/h was more than two times compared with most similar systems. Finally, stratified microbial community structures in the cathodes of the system were found. This gave evidence on the efficient catholyte recirculation which might facilitate nitrogen removal from wastewater. [ABSTRACT FROM AUTHOR]

To investigate the effect of the organic loading rate (OLR) on anaerobic treatment of monosodium glutamate (MSG) wastewater, a lab-scale up-flow anaerobic blanket (UASB) reactor was continuously operated over a 222-day period. The overall performances of COD removal and methane recovery initially exhibited an increase and subsequently decreased when the OLR was increased from 1 g-COD/L/d to 24 g-COD/L/d. At the optimal OLR of 8 g-COD/L/d, superior performance was obtained with a maximum COD removal efficiency of 97%, a methane production rate of 2.3 L/L/d, and specific methanogenic activity of 86 mg-CH 4 /g-VSS/d (feeding on glutamate), with superior characteristics of sludge in VSS concentration, average diameter of granules, and settling velocity. According to the results of the specific methanogenic activity, the methanogenic pathway was more inclined to pass through acetate than through hydrogen. Methanosarcina instead of Methanosaeta , with Methanobacterium and greatly increased Firmicutes, dominated in the UASB reactor after long term operation. These results support that the OLR had a substantial effect on both the treatment and energy recovery efficiency of MSG wastewater as well as on microbial community variations in the UASB reactor. Image 1 • Methanogenic degradation of monosodium glutamate wastewater was validated. • Optimal COD removal and CH 4 recovery performance was obtained at OLR below 8 g/L/d. • Maximal glutamate removal capacity of the UASB reactor reached 18 g-COD/L/d. • Methanobacterium and Methanosarcina were dominated after long-term operation. • The OLR had a substantial impact on the microbial community variations in the UASB. [ABSTRACT FROM AUTHOR]

Abstract This study introduced a novel dual-anode assembled microbial desalination cell to enhance the performance of domestic wastewater treatment. Two parallel units were fabricated with two anodes and one cathode, which is separated by two ion exchange membrane stacks. A hollow fiber membrane module was inserted in the cathode to intercept suspended solids and microbes. Based on preliminary experiments where synthetic wastewater was utilized, anode hydraulic retention time of 10 h and cathode aeration rate of 0.16 m3/h were chosen as the operating conditions. By innovatively connecting four membrane stacks in cascades, which multiplied flow rate without adding extra circulation pumps, the desalination rate of the system was improved 214.8% compared with single membrane stack mode. When modified domestic wastewater was applied, the average removal efficiencies of chemical oxygen demand, ammonia nitrogen, total nitrogen and total phosphorous reached 96.9%, 99.0%, 98.0% and 98.3%, respectively. Highlights • A novel duel-anode microbial desalination cell was fabricated. • Connecting four membrane stacks of MDC in cascades improved desalination efficiency. • Practicability of the novel MDC was evaluated with modified domestic wastewater. [ABSTRACT FROM AUTHOR]

To upgrade a wet flue gas desulfurization (FGD) wastewater treatment process in a typical thermal power plant (TPP) in Hunan province, China, a new concept for reusing polyaluminum chloride (PAC)- based water treatment plant sludge (WTPS) as a coagulant is proposed. Results show that, for an optimal WTPS dosage of 1,000 mg/L, the corresponding removal capacities for suspended solids (SS) and chemical oxygen demand (COD) from the practical FGD wastewater were 58.3% and 40.3%, respectively. Through an advanced treatment with a dosage of 50 mg/L of PAC, pH of 9, and stirring of 150 r/min for 60 s and 50 r/min for 15 min, the total removal efficiencies of SS, COD, and total cadmium (Cd) from the FGD wastewater were 93.7%, 88.8%, and 84.6%, respectively. Therefore, a new modification process (that involves mixing with WTPS - slag cleaner - neutralization - coagulation - sedimentation) was proposed. The proposed process is economically superior, and the average cost for the FGD wastewater treatment was only 1.08 USD/t. This could provide a cost-effective alternative process for upgrading FGD wastewater treatment facilities of TPPs. [ABSTRACT FROM AUTHOR]

Recovery of nutrient resources from the wastewater is now an inevitable strategy to maintain the supply of both nutrient and water for our huge population. While the intensive energy consumption in conventional nutrient recovery technologies still remained as the bottleneck towards the sustainable nutrient recycle. This study proposed an enlarged microbial nutrient recovery cell (EMNRC) which was powered by the energy contained in wastewater and achieved multi-cycle nutrient recovery incorporated with in situ wastewater treatment. With the optimal recovery solution of 3 g/L NaCl and the optimal volume ratio of wastewater to recovery solution of 10:1, >89% of phosphorus and >62% of ammonium nitrogen were recovered into struvite. An extremely low water input ratio of <1% was required to obtain the recovered fertilizer and the purified water. It was proved the EMNRC system was a promising technology which could utilize the chemical energy contained in wastewater itself and energy-neutrally recover nutrient during the continuous wastewater purification process. [ABSTRACT FROM AUTHOR]

A microbial fuel cell (MFC), as a cleaner wastewater treatment process, can recover electricity from organic wastes. However, high power production and high quality effluent are difficult to achieve simultaneously. In this study, a novel filtration composite anode (FCA), which combined carbon fiber brush and carbon textile was proposed to enhance COD removal and power generation performance of MFCs. The COD removal rate constant of MFCs with the filtration composite anode (FCA-MFC) was 0.33 h −1 , much higher than that of MFCs with single brush anode (FB-MFC) (0.23 h −1 ) or textile anode (FT-MFC) (0.18 h −1 ) in the recirculation mode, and also exceeded that of CA-MFC in non-recirculation mode (0.12 h −1 ). FCA-MFC delivered a maximum power density of 1140 mW m −2 at a recirculation rate of 2 mL min −1 , which was higher than the FB-MFC (990 mW m −2 ) and the FT-MFC (80 mW m −2 ) and its counterparts in non-recirculation mode (1000 mW m −2 ). Moreover, the FCA-MFC maintained a higher current density (4.0 A m −2 ) than the other two MFCs until the COD decreased to 40 mg L −1 at an external resistance of 100 Ω. CV and EIS tests verified a higher electrochemical performance of the filtration composite anode. These results demonstrated higher COD removals and power generation of the composite anode at ambient temperature, resulting from the filtration effect that facilitated mass transfer, increased microbial colonization, and improved electrochemical activity. Considering the high-quality effluent and high power generation, the filtration composite anode configuration promises a great potential for sustainable wastewater treatment application. [ABSTRACT FROM AUTHOR]

High energy consumption remains to be a key problem for application of membrane bioreactor (MBR). Optimization of MBR to save energy requires a compressive understanding of the performance of the reactor, among which the mixing performance is a significant parameter, however received little attention. In this study, a tracer experiment was carried out in a full-scale MBR for municipal wastewater treatment in China. The mixing performance of both the entire plant and the membrane tanks were evaluated. The entire plant was found to be a cascade of 2.15 continuous stirred tank reactors (CSTRs) with 8.02% of dead zones. The membrane tanks were also found to deviate from CSTR. The mixing energy was analyzed and compared with literature data from three aspects: the specific power used per unit of tank volume ( P s,v ), per unit of permeate volume ( P s,p ), and per unit of membrane area ( P s,m ). [ABSTRACT FROM AUTHOR]

In this study, a hollow fiber microfiltration membrane (HFM) coupled biocathode microbial desalination cell (MDC) was fabricated. With real wastewater flowing serially from anaerobic anode to oxic biocathode, filtered by the HFM and finally to the central membrane stack, the HFM-MDC took advantages of conventional anaerobic/oxic process, membrane biofilm reactor, and eletrodeionization technology, realizing advanced removal of organics, suspended solids, and salinity during 105 days of operation. The produced diluate was 86.1 v%, with final conductivity, chemical oxygen demand, total nitrogen, and total phosphorus (TP) reaching 59.2 ± 12.2 μS/cm, 35.5 ± 4.0 mg/L, 1.65 ± 0.39 mg/L, and 0.14 ± 0.05 mg/L respectively. The corresponding concentrate (13.9 v%) concentrated 6.7 times the initial conductivity (6044 ± 168 μS/cm), recovered 98.7% of phosphorous (TP of 40.9 ± 4.9 mg/L) and part of nitrogen. In addition, the HFM was stably operated for 105 days due to coefficient aeration flushing and regular chemical backwashing, with trans-membrane pressure keeping at ≤ 15 kPa for most of time. Moreover, this integrated process only needs wastewater as sole water input, and possesses a relative cheap HFM coupled biocathode compared with conventional Pt cathode, providing a promising solution for practical application of MDC in wastewater purification. [ABSTRACT FROM AUTHOR]

Utilization of two-electron oxygen reduction reaction (ORR) in bioelectrochemical systems (BES) is a novel way to generate H 2 O 2 from wastewater, and cathode catalyst is a key factor affecting ORR performance. Here, the catalytic performance of plain graphene, oxidized graphene and graphene oxide (GO) in microbial fuel cells (MFCs) and the influence of oxygen-containing functional groups are reported. Oxidized graphene air-cathode had 78% and 131% higher H 2 O 2 productions than plain graphene cathode respectively in an abiotic reactor and an MFC. GO showed nearly no H 2 O 2 production in the tests. XPS revealed that oxygen atomic fraction of oxidized graphene reached 5.7%, mostly in the form of C O C. These results show that oxidized graphene had good catalytic performance for H 2 O 2 production, and oxygen-containing functional groups, especially C O C could significantly enhance its performance, but overoxidation worked adversely. Meanwhile, using oxidized graphene air-cathode could realize simultaneous wastewater treatment, power output and H 2 O 2 generation in MFCs. [ABSTRACT FROM AUTHOR]

Wastewater containing abundant organics and nutrient resources requires large energy input in conventional treatment technologies to reach the discharge standard and/or to recover nutrient resources. This study presents a self-sustaining advanced wastewater purification and in situ nutrient recovery process accomplished by a newly designed 10-liter-scale bioelectrochemical system containing membrane stack configuration, which was called an advanced microbial nutrient recovery cell (AMNRC). After subsequent treatments in the AMNRC’s anode, cathode and stacked desalination chambers, all the removals of organics and nutrient in the domestic wastewater were achieved higher than 95%, which represented <24.9 mg/L of chemical oxygen demand, <14.2 mg/L of total nitrogen (TN), <6.5 mg/L of ammonium nitrogen (NH 4 + -N), and <0.49 mg/L of total phosphorus (TP) were left in the final effluent. Three sequential treatment processes including anaerobic microbial degradation, aerobic microbial treatment, and electrical ion migration comprehensively facilitated the above removals. Meanwhile TN, NH 4 + -N and TP were concentrated in the recovery solution by 260%, 150%, and 490%, respectively. Ammonium and phosphate were then recovered as struvite during crystallization. The AMNRC was proved as an energy neutral approach to efficiently purify wastewater and simultaneously recover nutrient, the treatment processes were driven by the energy extracted from wastewater itself. [ABSTRACT FROM AUTHOR]

• Conductivity is a comparable metric to characterize EET. • Nanowires and microbial aggregates have substantially different conductivity levels. • Several factors can cause a large variability in the measured conductivity. • Calculating the EET flux in microbial aggregates from conductivity measurement. Microbial extracellular electron transfer (EET) plays a crucial role in bioenergy production and resource recovery from wastewater. Interdisciplinary efforts have been made to unveil EET processes at various spatial scales, from nanowires to microbial aggregates. Electrical conductivity has been frequently measured as an indicator of EET efficiency. In this review, the conductivity of nanowires, biofilms, and granular sludge was summarized, and factors including subjects, measurement methods, and conducting conditions that affect the conductivity difference were discussed in detail. The high conductivity of nanowires does not necessarily result in efficient EET in microbial aggregates due to the existence of non-conductive substances and contact resistance. Improving the conductivity measurement of microbial aggregates is important because it enables the calculation of an EET flux from conductivity and a comparison of the flux with mass transfer coefficients. This review provides new insight into the significance, characterization, and optimization of EET in microbial aggregates during a wastewater treatment process. [ABSTRACT FROM AUTHOR]

A novel stacked microbial fuel cell (MFC) which had a total volume of 72 L with granular activated carbon (GAC) packed bed electrodes was constructed and verified to present remarkable power generation and COD removal performance due to its advantageous design of stack and electrode configuration. During the fed-batch operation period, a power density of 50.9 ± 1.7 W/m 3 and a COD removal efficiency of 97% were achieved within 48 h. Because of the differences among MFC modules in the stack, reversal current occurred in parallel circuit connection with high external resistances (>100 Ω). This reversal current consequently reduced the electrochemical performance of some MFC modules and led to a lower power density in parallel circuit connection than that in independent circuit connection. While increasing the influent COD concentrations from 200 to 800 mg/L at hydraulic retention time of 1.25 h in continuous operation mode, the power density of stacked MFC increased from 25.6 ± 2.5 to 42.1 ± 1.2 W/m 3 and the COD removal rates increased from 1.3 to 5.2 kg COD/(m 3 d). This study demonstrated that this novel MFC stack configuration coupling with GAC packed bed electrode could be a feasible strategy to effectively scale up MFC systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Applying electric field suppressed membrane fouling rate of AnMBR. • Applying electric field decreased the deposition of organic foulants on membrane. • Contribution of electrophoresis to membrane fouling suppression was quantified. • Applying electric field improved mixed liquor filterability of AnMBR. • Mechanism of mixed liquor filterability improvement was analyzed. Anaerobic membrane bioreactor (AnMBR) is a promising technology for wastewater treatment. However, membrane fouling as an inevitable challenge restricts its application. Recently novel membrane fouling control technology by applying electric field in AnMBR showed its economics and effectiveness. Nevertheless, the mechanism of fouling suppression is still unclear, limiting the development of this technology. In this study, electro-AnMBR was constructed. Long-term running showed that applying electric field of 0.5 V suppressed the membrane fouling evolution rate by nearly 23% and reduced the organic foulants on membrane by nearly 10%. To clarify the mechanism of fouling suppression, the contribution of electrophoresis to membrane fouling suppression was quantified by theoretical calculation for the first time. Results showed that electrophoresis was approximately equivalent to backwash with a flux of 0.56 L/(m2·h). Besides, impact of electric field on mixed liquor filterability of AnMBR was first investigated by dead-end filtration. Results presented that electric field reduced the filtration resistance of mixed liquor by nearly 77%. Then mixed liquor properties analysis, electrochemical oxidation simulation tests and metagenomic analysis revealed that electric field might improve mixed liquor filterability by bioelectrochemical oxidation. Finally, novel mechanism of electric field suppressed membrane fouling was elucidated, including electrophoresis to drive off the foulants and mixed liquor filterability improvement. This study might contribute to better understanding for membrane fouling control by applying electric field in AnMBR, and was meaningful for technical development. [ABSTRACT FROM AUTHOR]

• Summary of cutting-edge researches on microbial electrochemical sensor. • Discussion versatility and limitations of the traditional bioanode sensing element. • Highlight to explore spatial structure and interfacial electrochemical characteristics. • Suggestions for improving the bioavailability of toxic agents. • Potential challenges in field test for water biotoxicity monitoring. The development of low cost, convenient, and efficient biosensors is critical for water biotoxicity monitoring. Microbial electrochemical sensors employ electrode-biofilm as the sensing element, and detect biotoxicity by tracking the electron transfer between electroactive microorganisms and electrodes under toxic stress. Use of such biosensors in the aquatic environment can provide an early warning for the presence of various toxicants. In this paper, cutting-edge studies on strategies to create high performance microbial electrochemical biosensors are reviewed, which have mainly focused on different sensing elements. Bioanode sensing element-based microbial electrochemical sensors have been successfully applied in the laboratory to detect various toxicants, and to diagnose typical anaerobic wastewater treatment processes. The abiotic cathode sensing element is also included, which is mainly based on the electrochemical reduction of target analytes or its inhibition of the oxygen reduction reaction (ORR). The biocathode sensing element successfully solves the problems of low sensitivity and high false-negative rate, and recent advances and future perspectives in this field are highlighted. The limitations and potential solutions associated with the practical application of microbial electrochemical sensors for water biotoxicity monitoring are discussed. [ABSTRACT FROM AUTHOR]

The knowledge about membrane biofouling evolution in full-scale membrane bioreactor (MBR) applications is quite lacking, notwithstanding a few lab-scale investigations. For the first time, this study elaborated the effect of online NaOCl cleaning on the dynamic development of membrane biofilm microbiota during long-term operation of a large-scale MBR for municipal wastewater treatment (40,000 m3/d). Four times of membrane autopsies were conducted during 160 days operation to scrutinize the microbial community and concomitant organic foulants. The transmembrane pressure difference (TMP) development revealed limited effect of 30 min online NaOCl cleaning on long-term biofouling removal. NaOCl not only altered the structure of biofilm communities but also increased the richness and evenness on early fouling stages. Meanwhile, network analysis revealed the keystone taxa f_Comamonadaceae that played key roles in stabilizing community structure and developing anti-cleaning and irreversible fouling propensity of the biofilm. NaOCl cleaning also impacted the evolving of keystone taxa by intensifying the competition between the dominated taxa f_Moraxellaceae and other species during early fouling stages. Furthermore, the succession of the biofilm microbiota synchronously accelerated the TMP increase and the accumulation of organic foulants including polysaccharides, aromatic proteins and soluble microbial products during biofilm maturation. These identified key stubborn foulants shed light on limitations of current online NaOCl cleaning and provide guidance to optimize the efficiency of online chemical cleaning protocols in full-scale MBR operations. Image 1 • Membrane microbiota evolved in response to online NaOCl cleaning in long-term run. • Biofilm diversity was initially susceptible to cleaning but matured in later stages. • Biofilm communities harbored keystone taxa differing from lab-scale studies. • Taxa Comamonadaceae governed the biofilm network structure for anti-cleaning. • Organic foulants that synergized with the stubborn core-microbiota were explored. [ABSTRACT FROM AUTHOR]