COMPARISON OF GIARDIA-LAMBLIA AND GIARDIA-MURIS CYST INACTIVATION BY OZONE

Inactivation of Giardia lamblia and Giardia muris cysts was compared b y using an ozone demand-free 0.05 M phosphate buffer in bench-scale ba tch reactors at 22-degrees-C. Ozone was added to each trial from a con centrated stock solution for contact times of 2 and 5 min. The viabili ty of the control and treated cysts was evaluated by using the C3H/HeN mouse and Mongolian gerbil models for G. muris and G. lamblia, respec tively. The resistance of G. lamblia to ozone was not significantly di fferent from that of G. muris under the study conditions, contrary to previously reported data that suggested G. lamblia was significantly m ore sensitive to ozone than G. muris was. The simple Ct value for 3 lo g unit inactivation of G. lamblia was 2.4 times higher than the Ct val ue recommended by the Surface Water Treatment Rule.