The impact of conventional water treatment processes on cells of the cyanobacterium Microcystis aeruginosa

Cyanobacteria can produce toxins, tastes and odors which significantly impair water quality. Removal of intact cyanobacterial cells with their intracellular compounds during water treatment would potentially reduce the concentration of taste, odor and toxic cell metabolites present in the treated water. In this study, the effect of conventional water treatment processes using aluminum sulphate (alum) on the integrity of cells of toxic Microcystis aeruginosa was evaluated using both jar tests and pilot plant studies. Removal of M. aeruginosa cells by alum flocculation using a jar test apparatus indicated all cells were removed without damage to membrane integrity. Thus the chemical treatment and mechanical action did not damage the cultured M. aeruginosa cells and, more importantly, did not result in additional release of cell metabolites above background concentrations. For pilot plant experiments, which consisted of coagulation/flocculation–sedimentation–filtration, most of the cells were removed intact and no additional microcystin was found in the finished water.