The growth and physiological activity of Microcystis aeruginosa after flocculation using modified tannin

Abstract The aim of this study is to investigate the growth of Microcystis aeruginosa after flocculation using modified tannin (Q-TN). The cell biomass and percentage of living cells in the supernatant and settled flocs were investigated. Physiological activity of algal flocs were also evaluated. The results showed that the algae biomass in the supernatant increased in the first 18 days and declined in the following 12 days. The cell growth in the settled flocs was inhibited after 10 days. The contents of superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), and ascorbic acid (A S A) increased to the maximum on the 2–5 days for scavenging excess oxygen free radicals. The dehydrogenase and alkaline phosphatase (AKP) activity also reached the maximum on the 2–5 days. The malondialdehyde (MDA) content reached the highest on the 10th day, revealing the severe lipid peroxidation and cell lysis. The Q-TN exerted greater stresses on cells than Al 2 (SO 4 ) 3 .