Synergistic effect of ferrate (VI)-ozone integrated pretreatment on the improvement of water quality and fouling alleviation of ceramic UF membrane in reclaimed water treatment.

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]