The efficiency of combined coagulant and ballast to remove harmful cyanobacterial blooms in a tropical shallow system

Author(s)

Miranda, Marcela ; Noyma, Natalia ; Pacheco, Felipe S. ; de Magalhaes, Leonardo ; Pinto, Ernani ; Santos, Suzan ; Soares, Maria Fernanda A. ; Huszar, Vera L. ; Lurling, Miguel ; Marinho, Marcelo M.

• Document type: Journal article
• Source: HARMFUL ALGAE; v. 65, p. 27-39, MAY 2017.
• Web of Science Citations: 10

Abstract

We tested the hypothesis that a combination of coagulant and ballast could be efficient for removal of positively buoyant harmful cyanobacteria in shallow tropical waterbodies, and will not promote the release of cyanotoxins. This laboratory study examined the efficacy of coagulants {[}polyaluminium chloride (PAC) and chitosan (made of shrimp shells)] alone, and combined with ballast (lanthanum modified bentonite, red soil or gravel) to remove the natural populations of cyanobacteria collected from a shallow eutrophic urban reservoir with alternating blooms of Cylindrospermopsis and Microcystis. PAC combined with ballast was effective in settling blooms dominated by Microcystis or Cylindrospermopsis. Contrary to our expectation, chitosan combined with ballast was only effective in settling Cylindrospermopsis-dominated blooms at low pH, whereas at pH >= 8 no effective flocculation and settling could be evoked. Chitosan also had a detrimental effect on Cylindrospermopsis causing the release of saxitoxins. In contrast, no detrimental effect on Microcystis was observed and all coagulant-ballast treatments were effective in not only settling the Microcystis dominated bloom, but also lowering dissolved microcystin concentrations. Our data show that the best procedure for biomass reduction also depends on the dominant species. (C) 2017 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 14/06556-3 - Influence of land use changes in the nitrogen cycle in aquatic systems: a catchment scale approach
• Grantee: Felipe Siqueira Pacheco
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 14/50420-9 - Secondary metabolites from aquatic microrganisms and their impact on seafood and freshwater fish aquaculture
• Grantee: Ernani Pinto Junior
• Support Opportunities: Regular Research Grants