Effect of pre-chlorination on Microcystis aeruginosa cell integrity and microcystins removal

ABSTRACT

High nutrient input into waterbodies increases potentially toxic cyanobacteria blooms. Pre-chlorination treatment is excellent for cyanobacterial cell inactivation and dissolved cyanotoxins removal in water supply sources. This study aims to evaluate the pre-chlorination effect treatment on Microcystis aeruginosa cell integrity and its hepatotoxins (microcystins, MC) release and degradation on a laboratory scale. Loss of cell integrity is observed with increasing chlorine concentration. The maximum cell permeability without cell disintegration occurs at 2.5 mg Cl₂ L⁻¹. Degradations up to 70% and chlorophyll-a reductions over 70% are observed after 60 min exposure, with complete degradation at 2.5 and 3 mg Cl₂ L⁻¹. However, chlorine (Cl₂) exposure over 40.66 mg min L⁻¹ is required for microcystins MC-LR (i.e. radicals: leucine (L) and arginine (R)) and MC-RR (i.e. radicals: arginine and arginine) oxidation oxidation to concentrations below the legislation value for water potability.

KEYWORDS:

• Cyanobacteria toxic blooms
• cyanotoxins
• drinking water
• pre-chlorination
• water quality

Acknowledgements

This work was supported by the São Paulo Research Foundation (FAPESP) under grants n. 2010/50739-4 2011/51950-3, and 2014/50420-9; the University of São Paulo under grant n. 2021.1.307.64.8; the Higher-Level Personnel (CAPES) under grants n. 88882.327696/2019-01 and 88887.483720/2020-00, University of São Paulo—USPSusten Program of the Superintendence of Environmental Management (Supplementary Notice DOE 13 July 2022). We thank Dr. Fabyana Maria dos Anjos and Dr. Renata Albuquerque for the experimental design and sample preparation for the flow cytometry experiments.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the São Paulo Research Foundation [2010/50739-4 2011/51950-3]; University of São Paulo [USPSusten Program of the Superintendence of Environmental Management (Supplementary Notice DOE 13 July 2022)]; University of São Paulo [2021.1.307.64.8].