Immediate and Long-Term Impacts of Potassium Permanganate on Photosynthetic Activity, Survival and Microcystin-LR Release Risk of Microcystis Aeruginosa

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The immediate and long-term impacts of potassium permanganate (KMnO 4 ) as pre-oxidant on Microcystis aeruginosa and microcystin-LR (MC-LR) release risk were investigated. The cell density and the integrity of M. aeruginosa were determined by a flow cytometry, and typical photosynthetic parameters were measured by a pulse amplitude modulated fluorometer. The photosynthetic parameters were reduced to different degrees, accompanied with slight cytoclasis and complete degradation of extracellular MC-LR immediately after various dosages KMnO 4 oxidation (2-20mgL -1 ). In a 6-d cultivation following 5mgL -1 KMnO 4 oxidation, the cell density decreased from 3.9×10 6 to 0.6×10 6 cellsmL -1 , and then increased to 0.9×10 6 cellsmL -1 , while the extracellular MC-LR increased from 0 to 51.2μgL -1 . In the cultivation after 10mgL -1 KMnO 4 treatment, the intracellular MC-LR and cell activity significantly declined, while significant cytoclasis (cell density from 3.8×10 6 to 0cellsmL -1 ) and MC-LR release (increase from 0 to 15.2μgL -1 ) were observed. The photosynthetic parameters were found to be useful tools to predict the recovery tendency of M. aeruginosa cells, and the MC-LR release risk should be considered during KMnO 4 pre-oxidation in water-treatment plants.



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