Cyanobacteria (blue-green algae) produce toxins and tastes and odors that can
significantly impair water quality. The removal of cyanobacterial cells without
cell damage could significantly reduce the concentration of tastes, odors, and
toxic cell metabolites present in treated water. Cultured cyanobacterium,
hepatotoxic Microcystis aeruginosa, was mixed with reservoir water to simulate
water entering a treatment plant during an algal bloom. A bench-top jar-test
apparatus (flocculation) and a full-scale pilot plant
(flocculation-sedimentation-filtration) rated at 600 mL/min were used to evaluate
the effectiveness of conventional water treatment processes in removing
cyanobacterial cells. Removal of cells by flocculation using a jar-test apparatus
with aluminum sulfate dosed at concentrations used in water treatment practice
varied between 70 and 83%. Results obtained from the pilot experiment indicated
99.9% of the cells were removed. More important, no additional release of
microcystin (toxin) was found in the finished water. Includes 37 references, tables, figures.