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The integrated process of ozonation coupled with ceramic membrane filtration has been actively utilized to alleviate membrane fouling in water/wastewater treatment, however, the effect of ozonation on protein-based ceramic membrane fouling is still contradictory. Herein, for the first time, we reported the severe protein-based ceramic membrane fouling at high ozone dosage in the integrated process of ozonation coupled with ceramic membrane filtration and the related fouling mechanism was systematically explored. Ozonation at low dosage slightly mitigated membrane fouling, whereas severe membrane fouling occurred at high ozone dosage (10 mg/L for pre-ozonation; 4 and 10 mg/L for in-situ ozonation). At high ozone dosage, the trans-membrane pressure (TMP) remarkably increased (> 40 kPa) within 90 min and both hydraulically reversible and irreversible fouling contributed to the total membrane fouling resistance. Electro kinetic potential and particle size of the bovine serum albumin (BSA) solution were not the key factors affecting the aggravated membrane fouling at high ozone dosage. The remarkably deteriorated membrane fouling at high ozone dosage can be accounted for the formation of BSA crosslinks ascribed to the oligomerization and agglomeration of BSA and the intermolecular disulfide bridge formation with the crosslinks progressively accumulating on the membrane surface and in the membrane pores during filtration. The modeling results confirmed that the BSA-based membrane fouling mechanism was changed from cake-intermediate to cake-standard with ozonation at high ozone dosage. Meanwhile, the cake layer and/or gel layer played a more important role for the aggravated membrane fouling at high ozone dosage even though the contribution of pore blocking was also significant. [ABSTRACT FROM AUTHOR]

The effect of mixed liquor properties changed by ozonation especially with high dosages on membrane fouling is very complex and remains unclear. In this study, the effect of mixed liquor properties changed by ozonation especially with high dosages on ceramic ultrafiltration (UF) membrane fouling in wastewater treatment and the corresponding mechanism were systematically studied by characterization of the mixed liquor properties, hydraulic performance, the fouling layers and modeling at different ozone dosages (0, 2, 5, 10 mg/L). The membrane filterability of the mixed liquor after pre-ozonation (⩽5 mg/L) was enhanced and the corresponding membrane fouling was mitigated. After pre-ozonation, activated sludge had the better settleability and larger floc size. Meanwhile, there was a remarkable reduction of dissolved organic carbon (DOC), soluble microbial products (SMP) and extractable extra-cellular polymeric substances (EPS) after pre-ozonation and the removed organics were mainly belonged to the high molecular weight (MW) (1–10 kDa) and very high MW (10–200 kDa) substances. Intermediate blocking was the main membrane fouling during the mixed liquor filtration process and the best fouling mitigation performance was achieved for the sample with an intermediate ozone dosage of 5 mg/L (1.7 mg-ozone/g-mixed liquor suspended solids (MLSS)). Meanwhile, the water quality of permeate was even better after pre-ozonation (⩽5 mg/L) with the lower DOC and total nitrogen (TN) concentrations. Severe cell lysis occurred with the significant increase of the released organics in the mixed liquor and the activated sludge had smaller floc size and worse settleability when the pre-ozonation dosage was above 10 mg/L, which in turn resulted in the deteriorated membrane fouling control performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ceramic membrane (CM) market is growing with many full-scale applications. • CM is superior to polymeric membrane–high stability & flux, long life, low fouling. • Physicochemical processes (e.g., ozonation) are effective for fouling control. • Catalytic (nano) CMs can enhance antifouling, and pollutant removal capability. • Cost analysis of CMs, fouling control & cleaning should be evaluated at full-scale. Application of ceramic membrane technology in water and wastewater is rapidly growing. Inherent advantages of ceramic membrane including chemical/thermal stability, low fouling propensity and long lifespan make ceramic membrane technology attractive, and the ceramic membrane market is expected to achieve a compound annual growth rate of 12%. Ceramic membranes could be integrated with advanced oxidation processes such as in-situ ozonation that cannot be applied in the case of polymeric membrane due to their potential degradation during long-term exposure. In addition, the hybrid-ceramic membrane processes such as ceramic membrane bioreactor are superior to polymeric counterparts due to higher flux, higher pollutant removal, lower fouling rate and higher cleaning efficiency. Although ceramic membrane has high capital cost, life-cycle costs of ceramic and polymeric plants are comparable. Notably, full-scale ceramic membrane water/wastewater treatment plants have been installed in many countries such as Japan, USA, Singapore and United Kingdom. Given the attractiveness of this technology, performance of ceramic membrane is critically reviewed with a focus on their applications in water and wastewater treatment under mild conditions. In addition, fouling mechanisms and control strategies are elucidated and are compared with polymeric membranes. Importantly, for the first time, the status of full-scale applications and market prospects of ceramic membranes are critically analysed to show their future potential. Lastly, future research directions such as development of cost-effective ceramic membranes, understanding the biofouling evolution and economic evaluation of physicochemical processes for fouling control are proposed. [ABSTRACT FROM AUTHOR]

Abstract The comparison of long-term ceramic membrane bioreactors (MBRs) without and with in-situ ozonation was investigated in this study in terms of membrane fouling, activated sludge, effluent quality and microbial community in wastewater treatment. The optimal dosage of in-situ ozonation for long-term MBR operation was firstly determined as 5 mg/L (0.66 mg-ozone/g-mixed liquor suspended solid (MLSS)) with the optimal filterability of mixed liquor. During the long-term filtration experiment, MBR-ozone with in-situ ozonation demonstrated its significantly alleviated ceramic membrane fouling performance compared with MBR-control without in-situ ozonation as a result of the enhanced filterability of mixed liquor and organic foulants removal from membrane surface by in-situ ozonation oxidation. Furthermore, ozonation was beneficial to phosphorus removal and the total phosphorus (TP) concentration in effluent of MBR-control (0.82 ± 0.63 mg/L) was >2-fold higher than that of MBR-ozone (0.29 ± 0.41 mg/L). The improved phosphorus removal performance by ozonation was due to the increased abundance of phosphate accumulating bacteria of Candidatus Accumulibacter in activated sludge. However, ozonation was detrimental to nitrogen removal mainly as a result of the inhibition of denitrification with the decreased relative abundance of denitrification genus of Dechloromonas in activated sludge. Overall, ceramic MBR with in-situ ozonation had not only significantly alleviated membrane fouling but also remarkably improved phosphorus removal performance. Graphical abstract Unlabelled Image Highlights • Long-term ceramic MBRs without and with in-situ ozonation were compared. • The optimal filterability of mixed liquor was achieved at ozone dosage of 5 mg/L. • In-situ ozonation significantly alleviated ceramic membrane fouling. • Ozonation was beneficial to phosphorus removal but detrimental to nitrogen removal. • Microbial community of activated sludge was significantly changed by ozonation. [ABSTRACT FROM AUTHOR]

Membrane fouling is an obstacle impeding the wide applications of ceramic membranes and organics are responsible for most of the membrane fouling issues in wastewater treatment. In this study, Fenton cleaning strategy was firstly proposed to clean ceramic membrane fouling in wastewater treatment. Fe2+ efficiently catalyzed fouling cleaning with H 2 O 2 (1.5%) to recover the filterability of ceramic membrane. The maximum ∆ TMP recovery (over 99%) was achieved at an optimal Fe2+ dosage of 124 mg/L after 6 hr of immersion cleaning. The total residual membrane fouling resistance decreased gradually from this optimum value as the Fe2+ dosage increased above 124 mg/L. The residual hydraulically reversible fouling resistance accounted for most of the membrane fouling and was basically removed (≤ 3.0 × 109 m−1) when Fe2+ dosages higher than 124 mg/L were used. The foulants responsible for the formation of a residual hydraulically reversible fouling layer (DOC (dissolved organic carbon), proteins, polysaccharides, EEM (fluorescence excitation-emission matrix spectra), SS (suspended solids), and VSS (volatile suspended solids)) were gradually removed as the Fe2+ dosage increased. These residual organic foulants were degraded from biopolymers (10–200 kDa) to low molecular weight substances (0.1–1 kDa), and the particle size of these residual foulants decreased significantly as a result. The strong oxidation power of hydrogen peroxide/hydroxy radicals towards organic foulants was enhanced by Fe2+. Fe2+ played a significant role in the removal of hydraulically reversible fouling and irreversible fouling from the ceramic membrane. However, Fe2+ (≥ 124 mg/L) increased the likelihood of forming secondary iron-organics aggregates. Unlabelled Image [ABSTRACT FROM AUTHOR]

The operational issues of low-pressure ultrafiltration (UF) membrane are associated with its long-term membrane fouling caused by organic and inorganic matters, especially in treating shale gas wastewater (SGW) with complex water compositions. Herein, the effect of ferrate (Fe(VI)) pretreatment on UF membrane fouling and water quality in treating SGW was systematically investigated. Fe(VI) pretreatment significantly mitigated membrane fouling and slightly improved the effluent quality. The hydraulically irreversible fouling index and the total fouling index decreased by 69%–87% and 58%–84%, respectively. The mechanism of membrane fouling mitigation was comprehensively analyzed by the classical pore blocking model, correlation analysis between membrane fouling index and water quality, and the extended Derjaguin-Landau-Verwey-Overbeek theory. The synergistic mechanisms of membrane fouling mitigation were as follows: (i) Macromolecular organic matters (high molecular weight humics and biopolymers) which would block the membrane pores were oxidized into low fractions organics and removed by Fe(VI); (ii) Fe(VI) pretreatment improved interaction free energy of cohesion of foulants-foulants making foulants more hydrophilic and stable, and increased interaction free energy of adhesion of membrane-foulants making it more difficult for foulants to deposit on the membrane surface. Fe(VI) pretreatment had huge potential in alleviating membrane fouling in treating SGW and other complex wastewater. [Display omitted] • Fe(VI) is combined with UF to treat shale gas wastewater for the first time. • Fe(VI) notably decreases TFI and HIFI by 58%–84% and 69%–87%, respectively. • Biopolymers and high MW humics are the main foulants causing membrane fouling. • XDLVO theory confirms fouling mechanism by analyzing adhesion/cohesion energies. [ABSTRACT FROM AUTHOR]