The effect of temperature on the efficacy of ozonation for inactivating Cryptosporidium parvum oocysts

Examination of the effects of water temperature on the inactivation of Cryp tosporidium parvum oocysts with ozone, ozonation experiments were conducted in a semi-batch mode with a wide temperature range of 3-30 degreesC. Inact ivation was assessed in terms of mice infectivity and in vitro excystation. The temperature dependency of the CT products by a reduction in infectivit y of 2 log(10) could be described successfully by the Arrhenius equation, 1 /CT=1.086X10(18) e(-12520/K) where CT is the integrated ozone concentration over the contact time (mg/min/L) and K is the Kelvin temperature of water. As for the reduction in viability assessed by the excystation assay, proto col B, the obtained regression equation, 1/CT=1.802X10(18)e(-12640/K) was a lmost identical to that observed for the infectivity. Thus, the CT products required for a 2 log(10) reduction in both infectivity and viability incre ased by an average factor of 4.2 for every 10 degreesC decrease in water te mperature. Additionally, our findings suggested that the viability, as dete rmined by protocol B, could substitute for animal infectivity in evaluating the effects of environmental factors on the efficacy of ozonation.