A review of Cryptosporidium removal by granular media filtration

The promulgation of such regulations as the Interim Enhanced Surface Water Treatment Rule (IESWTR) and the Long Term 2 ESWTR (LT2ESWTR) has pointed out the need for methods to compare the relative efficacy of treatment alternatives for removing Cryptosporidium during drinking water treatment. Until recently, little was known about Cryptosporidium removal by filtration during nonideal operating periods. Furthermore, with the exception of formalin-inactivated oocysts, no reliable, quantitative surrogate for live oocysts has been demonstrated for a variety of operational conditions and filtration regimes in the peer-reviewed literature. This article consolidates and updates the available information on Cryptosporidium removal by filtration, with a focus on optimal and suboptimal filtration performance.