Chlorine and ozone disinfection of Encephalitozoon intestinalis spores

David E. John, Charles N. Haas, Nena Nwachuku, Charles P. Gerba

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


Microsporidia are intracellular eukaryotic parasites which have the potential for zoonotic and environmental, including waterborne, transmission. Encephalitozoon intestinalis is a microsporidian pathogen of humans and animals and has been detected in surface water. It is also on the Contaminant Candidate List of potential emerging waterborne pathogens for the US EPA. We performed disinfection studies using chlorine and ozone on E. intestinalis spores with a cell-culture most-probable-number assay to determine infectivity. Chlorine experiments were performed at 5°C at pH of 6, 7, and 8 with 1 mg/L initial chlorine concentrations, while ozone experiments were performed at 5°C and pH 7 with initial ozone doses of 1 and 0.5 mg/L, both in buffered water. A derivation of Hom's model for disinfection kinetics under dynamic disinfectant concentrations was used to fit observed data and calculate concentration-time product (C*t) values. Chlorine C*t values varied with pH such that 99% (2-log10) C*t ranged from 12.8 at pH 6 to 68.8 at pH 8 (mg min/L). Ozone C*t values were approximately an order of magnitude less at 0.59-0.84 mg min/L, depending on initial concentration.

Original languageEnglish (US)
Pages (from-to)2369-2375
Number of pages7
JournalWater research
Issue number11
StatePublished - Jun 2005


  • Disinfection
  • Emerging pathogen
  • Inactivation
  • Microsporidia
  • Waterborne parasites

ASJC Scopus subject areas

  • Ecological Modeling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution


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