Design Criteria for Inactivation of Cryptosporidium by Ozone in Drinking Water

Literature on ozone inactivation of Cryptosporidium was critically reviewed and analyzed. A set of criteria was established for selecting data from diverse sources and experimental protocols with the objective of compiling comparable data. Several kinetic models were evaluated ranging from the 4-parameter Hom “Power Law model to the single parameter Chick model. No single kinetic model gave a “best fit” to all of the data sets. On a case-by-case basis, the “best fit” models included the 3-parameter incomplete gamma Horn model, the 2-parameter Chick-Watson model, and the one parameter Chick model. Temperature effects were obscured in the natural water data when analyzed as a single aggregate data set. However, three natural waters each analyzed at several temperatures provided temperature effects for natural waters. While the time required to achieve 2 logs kill at 1 mg/L was approximately doubled for each 10°C drop in temperature in die laboratory waters, in natural waters the time increased by a factor of 4.5. pH apparently had little effect between pH 6 and 8 in laboratory waters while in natural waters pH 6 may enhance inactivation. ”