Effect of filter media on cyst and oocyst removal

As part of a pilot-scale examination of filtration media at the Cincinnati (Ohio) Water Works, heat-inactivated Giardia cysts and Cryptosporidium oocy sts were spiked into surface water that had already undergone coagulation a nd sedimentation. This spiked water was then introduced into pilot-scale fi lters containing sand only, typical dual anthracite-sand, and deep dual ant hracite-sand media configurations. All of the media types used in this stud y demonstrated similar removal capabilities, with average cyst removal rang ing from 2.7 to >4.5 logs and average oocyst removal of 2.7-3.9 logs. Endos pore and polystyrene bead removals were similar to those of the protozoa, b ut turbidity and particle counts demonstrated substantially less removal ca pability.