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 H2O2 and KMnO4, 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 KMnO4 was greater than H2O2. 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 KMnO4 system
had a markedly different physical structure of fouling layer, with an apparent sub-layer of δ-MnO2 nanosheets
below a fouling sub-layer. The formation of the δ-MnO2 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 H2O2 fouling layer, while for the KMnO4
system, the manganese oxidizing bacteria (MOB; e.g., Pseudoxanthomonas) and metal-resistant genus Acidovorax, dominated the community.