Effect of ferrate pre-oxidation on algae-laden water ultrafiltration: Attenuating membrane fouling and decreasing formation potential of disinfection byproducts.

ABSTRACT

Effect of ferrate [Fe(VI)] pre-oxidation on improving FeCl3/ultrafiltration (UF) of algae-laden source water was investigated. Fe(VI) disrupted algae cells and the in situ formed ferric (hydr)oxides aggregated with cell debris. Particle size and zeta potential of algae increased by 20% and 55% on average, respectively, after treatment with 0.02 mM of Fe(VI). These variations facilitated the formation of algae-ferric floc. Fe(VI) degraded algal extracellular organic matter into lower molecular weight products (fulvic-like and humic-like substances). Membrane flux, reversible membrane resistance (Rr) and irreversible membrane resistance (Rir) were improved by 51%, 61%, and 52% in Fe(VI) (0.02 mM)/FeCl3/UF treatment group compared with FeCl3/UF treatment after three filtration cycles. Fe(VI)/FeCl3/UF removed more than 10% ~ 34% of the dissolved organic compounds (DOC) and 6% ~ 17% of the total nitrogen (TN) compared with FeCl3/UF. Due to the enhanced removal of DOC and TN, formation potential of 12 kinds of carbonaceous-disinfection byproducts (C-DBPs) and 7 kinds of nitrogenous-disinfection byproducts (N-DBPs) decreased by 32.5% and 22.5%, respectively. Fe(VI) pre-oxidant was effective for alleviating membrane fouling and reducing formation potential of DBPs in algal laden water treatment.