Outbreaks of cryptosporidiosis throughout the world, especially the massive outbreak in Milwakee in 1993 drew public attention to the quality of drinking water supplies and to the efficiency of water treatment methods. Cryptosporidiosis is a severe gastrointestinal disease caused by the transmissive form of Cryptosporidium parvum protozoan and its oocysts. Digestion of as few as 30 oocysts may be fatal to infants, elderly and immunocompromized persons. C. parvum oocysts are ubiquitous in untreated water and extremely resistant to harsh environmental conditions including standard water...