Particle Ripening, Removal and Breakthrough in Drinking‐Water Filtration: Implications for the Capture of Cryptosporidium and Giardia Cysts

Abstract

An increasing number of reported outbreaks of Cryptosporidiosis, associated with the water supply, have led to an upsurge in interest in particle analysis in drinkingwater treatment. This paper describes recent observations of rapid-gravity filter performance using particle-size distribution analysis. Experimental rapid sand filters were constructed and operated using a suspension of PVC particles, and samples for particle analysis were collected at several depths and various times during the filter cycle. Ripening and early breakthrough of Cryptosporidium oocyst size particles were observed during the study, and 1 p particles exhibited the worst capture efficiency. Flow disturbances were found to reduce particle-capture efficiency including Cryptosporidium and Giardia cyst sizes.