The Characteristics of AOM and Formation of DBPs: The Role of Molecular Weights and Hydrophobicity

This study investigates the impacts of algogenic organic matter (AOM) distribution characteristics, specifically molecular weight (MW) and hydrophobicity, on the formation of disinfection byproducts (DBPs) derived from Microcystis aeruginosa. This study focuses on both extracellular organic matter (EOM) and intracellular organic matter (IOM) and their contributions to DBP formation. AOM was divided into 12 fractions based on MW and hydrophobicity (transphilic, hydrophilic, and hydrophobic fractions). The results reveal that the hydrophobic fraction (HPO) contributes the most to IOM, while low-MW (<1 kDa) and high-MW (>100 kDa) organic matter are the main components of AOM. An analysis of fluorescent species indicates that humic acid-like and fulvic acid-like compounds derived from the hydrophilic fraction (HPI) of EOM and the hydrophobic fraction (HPO) of IOM are the dominant low-MW (<1 kDa) species. Additionally, aromatic proteins derived from HPO in both EOM and IOM are the dominant high-MW (>100 kDa) fluorescent species. This suggests that proteins or polysaccharides are the primary adsorbents on the membrane during ultrafiltration (UF), while the humic acid component is not significantly deposited. Furthermore, this study identifies that the >100 kDa HPO in IOM serves as the main precursor for trichloromethane (TCM), trichloroacetic acid (TCAA), and dichloroacetic acid (DCAA). In EOM, the precursor for the highest TCMFP (63.6 µg/mg-C) is the >100 kDa HPI, while the highest contribution to TCM (21%) is from the >100 kDa HPO. These findings provide crucial information for controlling DBPs derived from AOM through membrane filtration, particularly in eutrophic water environments.