Comparison of algal removal by coagulation with clays and Al-based coagulants

Coagulation with both metal coagulants and clays can effectively remove algal cells from water. Pre-polymerized inorganic coagulants (e.g., polyaluminium chloride, PACl) normally contain high positive charge and the charge neutralization is one of algal removal mechanisms by coagulation, then, a better performance of PACl in the removal of algae is expected. The excellent algal removal efficiency by bentonite (Bent) and montmorillonite KSF (Mont-KSF) was observed in this study but for the turbidity reduction, Bent did not perform as well as Mont-KSF and then the most suitable clay to be considered is Mont-KSF. It has been proposed that the maximum algal removal efficiency by clays would be achieved when the particle size of clays is close to that of algal cells. However, under this study conditions, the particle size alone does not correlate the good removal efficiency of Bent and Mont-KSF. It is thus proposed that the nature of microstructure of clay particles could contribute to good algal removal efficiency.