Targeting membrane fouling with low dose oxidant in drinking water treatment: Beneficial effect and biological mechanism.

• Low dose oxidant can abate membrane fouling in GDM filtration. • Biopolymers were removed from influent water by dosed oxidants. • Dosed oxidants significantly altered biofilm bacterial community structure. • Formed δ-MnO 2 nanosheets layer protected membrane pore from contamination. Membrane fouling is the principal factor that currently limits the performance of gravity-driven membrane (GDM) filtration systems in drinking water treatment. In this study, the benefits of applying a low dose (approximately 0.1 mg · L − 1 ) of environmentally benign oxidants, both H 2 O 2 and KMnO 4 , as a pretreatment to GDM filtration system has been evaluated in terms of reduced membrane fouling and treated water quality. While both oxidants improved permeate flux, the effect of KMnO 4 was greater than H 2 O 2. Both oxidants reduced the size of influent organic substances and those of large molecular weight (>20 kDa), such as biopolymers, disappeared. The thickness of the fouling layers was substantially reduced after oxidation, and the KMnO 4 system had a markedly different physical structure of fouling layer, with an apparent sub-layer of δ-MnO 2 nanosheets below a fouling sub-layer. The formation of the δ-MnO 2 nanosheets sub-layer appeared to protect the underlying membrane pores from contamination by influent organics. Oxidation pretreatment reduced the presence of proteins and polysaccharides in the fouling layers and significantly altered the bacterial community structures (p < 0.01) and decreased biodiversity. The microbial species that secreted amounts of extracellular polymeric substances (EPS), such as Xanthobacter, were not eliminated in the H 2 O 2 fouling layer, while for the KMnO 4 system, the manganese oxidizing bacteria (MOB; e.g., Pseudoxanthomonas) and metal-resistant genus Acidovorax, dominated the community. [Display omitted] [ABSTRACT FROM AUTHOR]