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Inorganic salts (e.g., FeCl 3 and FeSO 4) are typically added to membrane bioreactor (MBR) for achieving improved total phosphorus (TP) removal and hydraulic performance. However, at the iron dose (e.g., Fe to P molar ratio of 1–4) required for effective TP removal, severe irreversible membrane fouling could become a significant concern. In this context, intermittent in-situ ozonation was provided for the first time directly in the membrane tank of Fe(II)-dosed membrane bioreactor, and its effect on membrane fouling mitigation was assessed and elucidated. The basic effluent quality remained unaffected, indicating that in-situ ozonation had no detrimental effects. In addition, concentration of foulants and the relative abundance of biofilm-forming microbes were comparable in both the Fe-MBR and Fe/O 3 -MBR. Importantly, as compared to the Fe-MBR, a 33% reduction in membrane fouling was achieved in the Fe/O 3 -MBR. The enhanced filterability of mixed liquor and the scrubbing of the membrane surface by ozone with the direct/indirect oxidation of the deposited foulants contributed to membrane fouling mitigation in the Fe/O 3 -MBR. Meanwhile, trans -membrane pressure profiles of MBRs followed cake-intermediate fouling mechanism. This study demonstrates that provision of intermittent in-situ ozonation is a simple and attractive approach to extend the operation of iron-dosed MBR. [Display omitted] • Performance of in-situ ozonation combined with Fe-MBR (Fe/O 3 -MBR) was elucidated. • Abundance of biofilm-forming bacteria was comparable in both Fe- and Fe/O 3 -MBR. • Ozonation improved mixed liquor properties and delayed the onset of severe fouling. • Increased floc size and membrane scrubbing by ozone contributed to fouling control. • Cake-intermediate fouling was the fouling mechanism in both Fe- and Fe/O 3 -MBR. [ABSTRACT FROM AUTHOR]

The combined pretreatment of coagulation and ozonation is extensively adopted for water quality enhancement and membrane fouling reduction in wastewater reclamation. Herein, the integrated treatment of ferrate pretreatment and in-situ ozonation/ceramic membrane filtration on water quality improvement and fouling reduction of ceramic membrane in secondary wastewater effluent treatment was reported for the first time. The results showed that the hybrid treatment of ferrate pretreatment and in-situ ozonation greatly inhibited the generation of N-dimethyl nitrosamine (NDMA) and did not generate bromate. Meanwhile, the best removal efficiencies of low molecular weight (MW) organics (32.3%), humic-like substances (17.8%) and biopolymers (87.5%) in effluent were achieved by the combination of ferrate (0.15 mM) pretreatment and in-situ ozonation (10 mg/L). Moreover, the control sample (without any treatment) had a fouling transmembrane pressure (TMP) of 30.5 kPa after 7.0 h filtration under a constant flux of 90 L/(m2·h) while that was only 1.0 kPa by the hybrid treatment of ferrate (0.15 mM) pretreatment and in-situ ozonation (10 mg/L). Soluble microbial products (SMP)-like substances with high molecular weight (MW) of 20–2000 kDa were the main foulants and intermediate-standard fouling mechanism played a principal role during the membrane filtration process. Statistical analysis showed that dissolved organic carbon (DOC), UV 254 and protein had the greatest positive correlation (above 0.92) to the total fouling resistance, whilst turbidity displayed the greatest negative correlation (around −0.61) to the total fouling resistance. The remarkable fouling alleviation was due to the improved water quality and in-situ cleaning, which were contributed to the coagulation and oxidation by ferrate and in-situ ozonation. Image 1 • Ferrate pretreatment- in-situ ozonation greatly reduces ceramic membrane fouling. • NDMA and bromate are remarkably reduced by ferrate pretreatment- in-situ ozonation. • Intermediate-standard fouling is the main fouling mechanism. • DOC, UV 254 and protein are the most important positive factors to R t. • Fouling alleviation is due to the improved water quality and in-situ cleaning. [ABSTRACT FROM AUTHOR]