(128b) Kinetics of Flocculation of Cyanobacteria Using Alum and Moringa Biocoagulant

There is great interest in purifying water bodies contaminated by Microcystis aeruginosa, a cyanobacteria responsible for harmful algal blooms and the release of microcystin toxins. Flocculation is the preferred approach for separating these cells, and flocculants that are more environmentally benign than conventional metal salt coagulants are desired. The seeds and extracts of Moringa oleifera are known to be quite effective flocculants in purifying turbid water. However, a detailed investigation of the effect of flocculant dosing on the flocculation kinetics and the floc size, as well as the comparison of the flocculation properties of Moringa with alum, is lacking in the literature.

In the work reported herein, laser diffraction analysis was used to investigate the kinetics of flocculation of M. aeruginosa using M. oleifera in three forms: powdered seeds, aqueous extracts of the powdered seeds containing the active protein coagulant, and aqueous extracts of the deoiled seeds. The flocculation process was carried out at various concentrations of the cyanobacterial cells and the coagulant. The results are compared with those from similar experiments using alum as the coagulant. The laser diffraction data were analyzed for the time evolution of the floc’s size and fractal dimension, allowing the flocculation process to be investigated in much greater detail than possible using conventional turbidity measurements.