Removing Giardia Cysts From Low Turbidity Waters by Rapid Rate Filtration

Pilot‐plant studies showed that when effective chemical pretreatment is employed in combination with rapid rate filtration, removals of turbidity, total coliform bacteria, and Giardia cysts from low turbidity waters may be greater than 80, 99.9, and 99.9 percent, respectively. Proper coagulation, however, requires the careful selection of chemicals and dosages. It was also observed that for waters having turbidity levels <1 ntu, percent reduction of turbidity can serve as a surrogate indicator of the removal of Giardia cysts.