MODELING CHLORINE INACTIVATION REQUIREMENTS OF CRYPTOSPORIDIUM-PARVUMOOCYSTS

Chlorine and monochloramine inactivation of Cryptosporidium parvum ooc ysts was studied using bench-scale experiments in 0.05-M phosphate buf fer at pH 6 and 8 at 22 degrees C. Animal infectivity using neonatal C D-1 mice was used as the criterion for oocyst viability. Inactivation data were fitted to a robust kinetic model, the incomplete gamma Hom ( I.g.H.) which can account for first-order disinfectant decomposition. For chloramination a two-step disinfection approach was evaluated in w hich chlorine species were applied sequentially with free chlorine fol lowed by ammonium chloride and preformed monochloramine (if necessary) . Increasing levels of free chlorine pretreatment were shown to reduce the subsequent monochloramine concentration and/or contact time requi red for a given level of inactivation thereby demonstrating synergism. Incomplete gamma Hom models were used to generate design graphs that can aid engineers in establishing disinfection requirements for contro lling Cryptosporidium parvum in drinking water.