Impact of sonication on the algal organic matter characteristics of Anabaena circinalis, Microcystis aeruginosa, and Chlorella vulgaris

Abstract

The frequent occurrence of harmful algal blooms (HABs) in drinking water reservoirs causes water treatment and supply problems. Ultrasonication is a physicochemical treatment method used to treat HABs. During the ultrasonication of HABs, algal organic matter (AOM), including both extracellular organic matter (EOM) and intracellular organic matter (IOM), is released and changes the dissolved organic matter characteristics. In this study, Anabaena circinalis (A. circinalis), Microcystis aeruginosa (M. aeruginosa), and Chlorella vulgaris (C. vulgaris) were used to investigate changes in AOM characteristics during ultrasonication using a fluorescence excitation-emission matrix and assimilable organic carbon. We found that ultrasonication increased the dissolved AOM content, resulting in increased dissolved organic carbon from IOM released from algal cells. A. circinalis, M. aeruginosa, and C. vulgaris had dissolved organic carbon concentrations of 22.5, 3.8, and 6.7 mg/L before sonication, which increased to 29.1, 10.8, and 7.7 mg/L after ultrasonication, respectively. Additionally, the IOM released during ultrasonication held more protein-like substances and was mostly associated with biodegradable organic matter.