Inactivation of Cryptosporidium parvum oocysts with ozone and monochloramine at low temperature

The rate of Cryptosporidium parvum inactivation decreased with decreasing t emperature (1-20 degreesC) for ozone and for monochloramine applied alone a s well as after pre-treatment with ozone. Synergy was observed at all tempe ratures studied for the ozone/monochloramine sequential disinfection scheme . The synergistic effect was found to increase with decreasing temperature. The inactivation rate with monochloramine after ozone pre-treatment was 5 times faster at 20 degreesC and 22 times faster at 1 degreesC than the corr esponding post-lag phase rates of inactivation with monochloramine at these temperatures when no ozone pre-treatment was applied. The CT required for achieving 2-logs of inactivation ranged from 11 400 mg min l(-1) at 20 degr eesC to 64 600 mg min l(-1) at 1 degreesC when monochloramine was applied a lone. In contrast, the CT required for an overall sequential inactivation o f 2-logs ranged from 72.1 mg min l(-1) at 20 degreesC to 1350 mg min l(-1) at 1 degreesC when applying monochloramine after ozone pre-treatment. The p resence of excess ammonia in the monochloramine solutions was not responsib le for the synergy observed in ozone/monochloramine sequential disinfection . (C) 2000 Elsevier Science Ltd. All rights reserved.