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Open AccessArticle

Delayed Release of Intracellular Microcystin Following Partial Oxidation of Cultured and Naturally Occurring Cyanobacteria

Southern Nevada Water Authority (SNWA), P.O. Box 99954, Las Vegas, NV 89193-9954, USA
Water Research Australia (WaterRA), Adelaide, SA 5001, Australia
BGA Innovation Hub and Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales (UNSW), Sydney, NSW 2052, Australia
Department of Civil Engineering, McGill University, Montreal, QC H3A 0G4, Canada
Department of Civil Engineering, Saint Louis University, St. Louis, MO 63103, USA
Hazen and Sawyer, Raleigh, NC 27607, USA
Author to whom correspondence should be addressed.
Toxins 2020, 12(5), 335;
Received: 8 April 2020 / Revised: 6 May 2020 / Accepted: 13 May 2020 / Published: 20 May 2020
(This article belongs to the Special Issue Removal of Cyanobacteria and Cyanotoxins in Waters)
Oxidation processes can provide an effective barrier to eliminate cyanotoxins by damaging cyanobacteria cell membranes, releasing intracellular cyanotoxins, and subsequently oxidizing these toxins (now in extracellular form) based on published reaction kinetics. In this work, cyanobacteria cells from two natural blooms (from the United States and Canada) and a laboratory-cultured Microcystis aeruginosa strain were treated with chlorine, monochloramine, chlorine dioxide, ozone, and potassium permanganate. The release of microcystin was measured immediately after oxidation (t ≤ 20 min), and following oxidant residual quenching (stagnation times = 96 or 168 h). Oxidant exposures (CT) were determined resulting in complete release of intracellular microcystin following chlorine (21 mg-min/L), chloramine (72 mg-min/L), chlorine dioxide (58 mg-min/L), ozone (4.1 mg-min/L), and permanganate (391 mg-min/L). Required oxidant exposures using indigenous cells were greater than lab-cultured Microcystis. Following partial oxidation of cells (oxidant exposures ≤ CT values cited above), additional intracellular microcystin and dissolved organic carbon (DOC) were released while the samples remained stagnant in the absence of an oxidant (>96 h after quenching). The delayed release of microcystin from partially oxidized cells has implications for drinking water treatment as these cells may be retained on a filter surface or in solids and continue to slowly release cyanotoxins and other metabolites into the finished water. View Full-Text
Keywords: cyanobacteria; oxidation; stagnation; microcystin; water treatment; quenching cyanobacteria; oxidation; stagnation; microcystin; water treatment; quenching
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Greenstein, K.E.; Zamyadi, A.; Glover, C.M.; Adams, C.; Rosenfeldt, E.; Wert, E.C. Delayed Release of Intracellular Microcystin Following Partial Oxidation of Cultured and Naturally Occurring Cyanobacteria. Toxins 2020, 12, 335.

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