Integration of aerobic riverbank filtration and ultrafiltration for advanced water treatment and membrane ageing reduction

Abstract

Reduced chemical usage and the development of cost-effective water treatment technologies are key priorities for safeguarding public health, particularly in the context of global carbon neutrality goals. Integrating nature-based riverbank filtration (RBF) with ultrafiltration (UF) offers an efficient and environmentally friendly approach for drinking water supply. However, traditionally deployed RBF systems operating across aerobic, anoxic, and anaerobic zones face practical challenges, including ion release and groundwater depletion. Focusing solely on the aerobic RBF may address these limitations; however, its impact on UF performance, particularly in relation to natural organic matter (NOM) as a major membrane foulant, remains poorly understood. As microbe-mediated processes in RBF also critically influence membrane performance, this study examined aerobic RBF’s influence on UF membrane fouling through comprehensive NOM and microbial analyses. The results showed that aerobic RBF pretreatment reduced UF fouling by approximately 77%, primarily through decreased organic accumulation on membrane surfaces. This mitigation was attributed to reductions in dissolved organic carbon, UV254, humic acid-like substances, and soluble microbial products (e.g., proteins). NOM molecular analysis revealed decreased quantities of proteins, lignin/carboxylic-rich alicyclic molecules (CRAM)-like compounds, and condensed aromatic structures (CAS). Adsorption accounted mainly for the removal of persistent compounds (e.g., CAS), while the removal of proteins and lignin was attributed to microbially mediated biotransformation by genera such as Streptomyces and Pseudomonas. These findings provide novel molecular-level insights into the dynamics of NOM in RBF and demonstrate the significant potential of aerobic RBF as an effective pretreatment step for UF towards advanced water treatment applications.