Assessment of the risk of infection by Cryptosporidium and Giardia in non-potable reclaimed water

H. Ryu, Absar Alum, K. D. Mena, Morteza Abbaszadegan

Research output: Chapter in Book/Report/Conference proceedingChapter

46 Scopus citations


Quantitative risk assessment for Cryptosporidium oocysts and Giardia cysts was performed to determine the public health significance of non-potable use of tertiary treated reclaimed water. Seven reclaimed water treatment plants in the southwestern United States participated in this study. The average public exposure to oocysts and cysts was estimated, based on concentrations, recovery efficiency, viability and three exposure scenarios. The exponential dose-response model was chosen to determine the probability of infection from ingestion of various numbers of oocysts and cysts. The risks of infection for Giardia were approximately one or two orders of magnitude higher than those for Cryptosporidium. The combined risks of infection from oocysts and cysts at sites using a combination of chlorination and UV disinfection would meet the annual acceptable risk of 1.00E-04, whereas those at the other utilities using only chlorination indicated higher probability of infection than the 1.00E-04 resulting from accidental consumption of a small amount of non-potable reclaimed water.

Original languageEnglish (US)
Title of host publicationWastewater Reclamation and Reuse for Sustainability
EditorsI.S. Kim, S. Kim, J. Cho
Number of pages8
StatePublished - 2007

Publication series

NameWater Science and Technology
ISSN (Print)0273-1223


  • Cryptosporidium
  • Giardia
  • Risk assessment
  • Water reuse

ASJC Scopus subject areas

  • Environmental Engineering
  • Water Science and Technology


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