The efficiency of combined coagulant and ballast to remove harmful cyanobacterial blooms in a tropical shallow system |
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Affiliation: | 1. Post-Graduate Program in Ecology, Federal University of Juiz de Fora, R. José Lourenço Kelmer, Juiz de Fora, MG 36036-330, Brazil;2. Laboratory of Ecology and Physiology of Phytoplankton, Department of Plant Biology, University of Rio de Janeiro State, Rua São Francisco Xavier 524 – PHLC Sala 511a, 20550-900 Rio de Janeiro, Brazil;3. Earth System Science Center (CCST), National Institute for Space Research (INPE), Av. dos Astronautas, 1.758 – Jardim da Granja, 12227-010 São José dos Campos, SP, Brazil;4. Department of Clinical and Toxicological Analyses, School of Pharmaceutical Sciences, University of São Paulo, Av. Prof. Lineu Prestes, 580 – Bl 17, 05508-900 São Paulo, SP, Brazil;5. Laboratory of Phycology, National Museum, Federal University of Rio de Janeiro 20940-040, Rio de Janeiro, Brazil;6. Aquatic Ecology & Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands;7. Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, 6700 AB Wageningen, The Netherlands;1. State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China;2. College of Biology and Environment, Nanjing Forestry University, Nanjing 210037, China;3. Aquatic Ecology & Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands;4. Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, 6700 AB Wageningen, The Netherlands;1. Water Authority Brabantse Delta, P.O. Box 5520, 4801 DZ, Breda, The Netherlands;2. BMD Advies Rijndelta Environmental Consultancy, Ebweg 18, 2991 LT, Barendrecht, The Netherlands;3. Aquatic Ecology & Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA, Wageningen, The Netherlands;4. Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, 6700 AB, Wageningen, The Netherlands;1. Aquatic Ecology & Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands;2. Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, 6700 AB Wageningen, The Netherlands;3. Regional Water Authority Brabantse Delta, P.O. Box 5520, 4801 DZ Breda, The Netherlands;1. School of Water and Environment, Chang’an University, Xi’an 710054, PR China;2. Key Laboratory of Subsurface Hydrology and Ecology in Arid Areas, Ministry of Education, Xi’an 710054, PR China;1. Aquatic Ecology & Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA, Wageningen, The Netherlands;2. Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, 6700 AB, Wageningen, The Netherlands;3. Laboratory of Ecology and Physiology of Phytoplankton, Department of Plant Biology, University of Rio de Janeiro State, Rua São Francisco Xavier 524—PHLC Sala 511a, 20550-900, Rio de Janeiro, Brazil;4. Museu Nacional, Federal University of Rio de Janeiro, 20940-040, Rio de Janeiro, Brazil |
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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. |
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Keywords: | Eutrophication control Cyanobacteria mitigation Chitosan |
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