Mitigation of ultrafiltration membrane fouling by a simulated sunlight-peroxymonosulfate system with the assistance of irradiated NOM

Abstract

Oxidation pretreatments prior to ultrafiltration are hindered by the need for energy input and sludge disposal. Herein, a simulated sunlight-induced natural organic matter (NOM) for peroxymonosulfate (PMS) activation was used as pretreatment to alleviate ultrafiltration membrane fouling caused by NOM itself in the Songhua River water. When light intensity was over 100 mW/cm2, the pretreatment removed NOM effectively, characterized with UV254, dissolved organic carbon (DOC) and maximum fluorescent intensity (Fmax), and improved filtration flux. At 200 mW/cm2 light intensity and 0.5 mM PMS, 57.5% of UV254 and 18.5% of DOC were removed, and humic-like fluorescent component was degraded by 84%-94% while ∼60% for protein-like substance. Membrane flux was increased by 94%, and reversible and irreversible fouling resistances were reduced by 62.4% and 51.9%, respectively. Both total fouling index (TFI) and hydraulic irreversible fouling index (HIFI) were moderately correlated with the DOC, whereas they prominently correlated with the UV254 and the Fmaxs of all fluorescence components, which could be served as key indicators to predict and control membrane fouling. Mathematical modeling showed that the pretreatment alleviated the fouling in the membrane pores and cake layer. The simulated sunlight-induced NOM (3NOM* and eaq¯) could activate PMS to form active species, which enabled to oxidize high molecular weight (MW) substances and mineralize low MW compounds in NOM as well as hinder their linking with inorganic cations, thereby reducing organic and inorganic membrane fouling simultaneously. This study may provide a new strategy for decentralized potable water treatment, especially in a single household or community.