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Development of flotation and nanofiltration technologies to remove cyanobacteria and cyanotoxins in drinking water treatment
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Resumo(s)
Dissolved air flotation (DAF) and nanofiltration were optimised and integrated to remove
cyanobacteria and cyanotoxins from drinking water. The removal mechanisms of the most
commonly occurring cyanobacteria (cultured cells and aggregates of Microcystis aeruginosa
and Plankthotrix rubescens filaments) and cyanotoxins (hepatotoxic microcystins, and
neurotoxic anatoxin-a) were investigated, as well as the impact of the water background
organic (NOM) and inorganic matrixes, using both model and natural waters.
Results showed that coagulation/flocculation/DAF is the best process for clarifying
cyanobacterial-rich waters (93-99% chlorophyll a removal), without toxin release to water and
with lower NOM effect, using low recycle (8%), and lower coagulant doses, slower
coagulation, stronger but shorter flocculation than the conventional
coagulation/flocculation/settling.
Studies with a negatively charged tight nanofiltration membrane demonstrated that while
nanofiltration fluxes of low NOM and moderately hard water are largely influenced by the
background pH and calcium hardness, rather than by the type of NOM, anatoxin-a and
microcystins are efficiently removed (anatoxin-a by electrostatic interactions and steric
hindrance, microcystins mainly by steric hindrance), producing a final water of superior
quality, also in terms of NOM content, regardless of the variations in feed water quality (pH,
calcium hardness, NOM, toxins) and water recovery rate (up to 90%).
Descrição
Tese dout., Ciências e Tecnologias do Ambiente, Universidade do Algarve, 2006
Palavras-chave
Tecnologias do ambiente Nanofiltração Cianobactérias Cianotoxinas Água do consumo Matéria orgânica 504