Evaluating Sedimentation and Various Filter Media for Removal of Giardia Cysts

Abstract

The primary purpose of the pilot study described in this article was to evaluate the efficiency of sedimentation and of coarse anthracite media for removing Giardia cysts. Removal of cysts by sedimentation was observed to range from 65 to 93 percent and was generally similar to removal of turbidity. The coarse anthracite media produced water of inferior quality when alum was the only coagulant, but its performance was found to be improved by the use of a high‐molecular‐weight, slightly anionic polymer. Cyst concentrations appeared to be higher than usual during the initial phase of a filter run, indicating that a filter‐to‐waste period may be desirable. The authors conclude that effective control of Giardia cysts depends on informed application of the multiple‐barrier concept.