Effect of filter media on cyst and oocyst removal

Abstract

Spiking studies underscore the important role filtration plays in removing protozoa from surface water. As part of a pilot‐scale examination of filtration media at the Cincinnati (Ohio) Water Works, heat‐inactivated Giardia cysts and Cryptosporidium oocysts were spiked into surface water that had already undergone coagulation and sedimentation. This spiked water was then introduced into pilot‐scale filters containing sand only, typical dual anthracite–sand, and deep dual anthracite–sand media configurations. All of the media types used in this study demonstrated similar removal capabilities, with average cyst removal ranging from 2.7 to > 4.5 logs and average oocyst removal of 2.7–3.9 logs. Endospore and polystyrene bead removals were similar to those of the protozoa, but turbidity and particle counts demonstrated substantially less removal capability.