Sequential disinfection of Cryptosporidium parvum by ozone and chlorine dioxide

A two step disinfection approach was evaluated for control of Cryptosporidium parvum using bench-scale experiments in 0.05 M phosphate buffer at pH 8 and 22 degrees C. Sequential application of ozone and chlorine dioxide was evaluated where ozone was applied first followed by chlorine dioxide. Infectivity in neonatal CD-1 mice was used to assess oocyst viability after disinfection. The sequential treatment of oocysts by ozone followed by chlorine dioxide resulted in additional inactivation of C. parvum due to the synergism of the two disinfectants. The inactivation kinetics for chlorine dioxide were modeled following preconditioning with ozone at a given level using the Integral-Hem model which takes the disinfectant decay into account. These preliminary findings indicate that sequential disinfection with ozone followed by chlorine dioxide may have potential in controlling waterborne parasites.