Unraveling Membrane Fouling Induced by Chlorinated Water Versus Surface Water: Biofouling Properties and Microbiological Investigation

Chlorine is usually applied in the urban water treatment process to deactivate pathogens and prevent waterborne diseases. As a pre-treatment, it remains unclear whether chlorinated water can effectively alleviate membrane fouling during ultrafiltration(UF). In this study, tap water was investigated for its effect on biofilm formation and biofouling in a gravity-driven membrane(GDM) filtration system. For comparison, biofilm/biofouling with untreated surface(lake) water was studied in parallel. It was found that more severe membrane fouling occurred with the filtration of tap water than lake water, and larger quantities of polysaccharide and extracellular DNA(eDNA) were present in the tap-water biofilm than in the lake-water biofilm. The tap-water biofilm had a densely compact morphology. In contrast, a porous,spider-like structure was observed for the lake-water biofilm, which was assumed to be associated with the bacteria in the biofilm. This hypothesis was verified by 16S ribosomal RNA(rRNA) sequencing, which demonstrated that Xanthobacter was the dominant taxon in the tap-water biofilm. Additionally, membrane hydrophobicity/hydrophilicity played a minor role in affecting the membrane fouling properties and microbial community. This study revealed the significant role of chlorine-resistant bacteria in biofouling formation and provides a deeper understanding of membrane fouling, which can potentially aid in searching for effective ways of controlling membrane fouling.