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Abstract A novel ferrate (VI)-ozone integrated pretreatment process was proposed and applied herein for the first time in reclaimed water treatment. We demonstrated the synergistic effect of the ferrate (VI)-ozone integrated process in terms of •OH generation and its double-win effects on the improvement of water quality and fouling alleviation of ceramic ultrafiltration (UF) membrane. The concentration of •OH in the ferrate (VI) (0.15 mM)-ozone (10 mg/L) integrated case was almost 3-fold higher compared to the ferrate (VI) (0.15 mM) case, while no obvious •OH was detected in the pre-ozonation case (10 mg/L) in Milli-Q water. The reclaimed water quality was remarkably enhanced with the maximum removal efficiencies of 70.5% (DOC), 80.5% (UV 254), 25.6% (protein) and 65.5% (polysaccharide) in influent achieved by the integrated pretreatment of ozone (10 mg/L) and ferrate (0.15 mM). Biopolymers (molecular weight (MW) of 20–2000 kDa) were the main removed organics with the best removal efficiency of 92.6%. Additionally, membrane fouling was effectively mitigated and the normalized trans-membrane pressure (TMP) was maximally decreased by 89.5% obtained after the integrated pretreatment of ozone (10 mg/L) and ferrate (0.15 mM). The statistical analysis results demonstrated that the increased particle size and the effective reduction of organic matters with ferrate-ozone integrated pretreatment led to a porous fouling layer with high permeability and thus a remarkable reduction of TMP and resistances, which was also in agreement with the modeling results that cake blocking was significantly alleviated. Graphical abstract fx1 Highlights • The synergistic effect of ferrate-ozone with more •OH generated is confirmed. • Ferrate-ozone significantly improves the water quality of reclaimed water. • Ferrate-ozone pretreatment remarkably alleviates ceramic membrane fouling. • A more porous fouling layer is formed with ferrate-ozone pretreatment. • Cake-intermediate fouling is the main fouling mechanism. [ABSTRACT FROM AUTHOR]

Ferrate (VI) is a unique and “green” chemical that can be utilized for oxidation, disinfection and coagulation simultaneously in a single unit without producing by-product. Herein, for the first time, we reported the integrated process of ferrate (VI) pretreatment coupled with ceramic membrane reactor for mitigating membrane fouling in natural reclaimed water treatment. Membrane fouling was effectively mitigated by ferrate pretreatment with the maximum trans-membrane pressure (TMP) reduction of 81.8% achieved at ferrate dosage of 0.15 mM. Moreover, the fouling mechanism changed from intermediate-standard blocking to cake-intermediate blocking with ferrate pretreatment and the contribution of cake layer fouling was significantly diminished with increase of ferrate dosage (≤ 0.15 mM). Statistical analysis including redundancy analysis and clustering correlation analysis showed that chemical oxygen demand (COD), dissolved organic carbon (DOC) and polysaccharide were the most important positive factors to R t with their correlation coefficients above 0.92 while SS and turbidity were the most important negative factors to R t with their correlation coefficients below − 0.87. Long-term filtration experiments also confirmed the membrane fouling control performance by ferrate with the significant extension of the onset of membrane fouling. [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]