Characteristics of extracellular organic matters and the formation potential of disinfection by-products during the growth phases of M. aeruginosa and Synedra sp.

Extracellular organic matter (EOM) is an important precursor of disinfection by-products (DBPs). Nowadays, little is known about changes in molecular weight (MW) and hydrophilic (HPI)/hydrophobic (HPO) fractions of EOM during the entire algal growth phase. In this study, a combined approach of fractionation procedure and parallel factor (PARAFAC) analysis was applied to characterize the EOM during the entire growth phase of two algal species (M. aeruginosa and Synedra sp.), and investigated the relationships between fluorescent component and the DBP formation potential (FP) in MW and HPI/HPO fractions. Thereinto, three components (including one protein-like component (C1), one humic-like component (C2), and one fulvic acid-like component (C3)) were identified by the PARAFAC model. For two algae, the HPI and high MW (> 100 kDa) fractions were both the main components of algal EOM in the three growth phases in terms of the dissolved organic carbon. The high MW fraction had more C1 compared with other MW fractions, especially for M. aeruginosa. Besides, the formation risk of EOM-derived DBPs from M. aeruginosa was lower than that from Synedra sp. The result of this study showed the FP of DBPs varied with fluorescent components of algal EOM fractions and also indicated that the humic-like substances were tended to form trichloromethane and the tryptophan-like substances were associated with dichloroacetic acid by canonical correspondence analysis for both two algae.