Efficacy of Chlorine Dioxide Tablets on Inactivation of Cryptosporidium Oocysts
2014
Murphy, Jennifer L. | Haas, Charles N. | Arrowood, Michael J. | Hlavsa, Michele C. | Beach, Michael J. | Hill, Vincent R.
The ability of chlorine dioxide (ClO₂) to achieve 2-log inactivation of Cryptosporidium in drinking water has been documented. No studies have specifically addressed the effects of ClO₂ on C. parvum oocyst infectivity in chlorinated recreational water venues (e.g., pools). The aim of this research was to determine the efficacy of ClO₂ as an alternative to existing hyperchlorination protocols that are used to achieve a 3-log inactivation of Cryptosporidium in such venues. To obtain a 3-log inactivation of C. parvum Iowa oocysts, contact times of 105 and 128 min for a solution containing 5 mg/L ClO₂ with and without the addition of 2.6 mg/L free chlorine, respectively, were required. Contact times of 294 and 857 min for a solution containing 1.4 mg/L ClO₂ with and without the addition of 3.6 mg/L free chlorine, respectively, were required. The hyperchlorination control (21 mg/L free chlorine only) required 455 min for a 3-log inactivation. Use of a solution containing 5 mg/L ClO₂ and solutions containing 5 or 1.4 mg/L ClO₂ with the addition of free chlorine appears to be a promising alternative to hyperchlorination for inactivating Cryptosporidium in chlorinated recreational water venues, but further studies are required to evaluate safety constraints on use.
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