Cryptosporidium monitoring system at a water treatment plant, based on waterborne risk assessment

Y. Masago, K. Oguma, H. Katayama, T. Hirata, S. Ohgaki

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


The water volume required for daily monitoring of Cryptosporidium (which can statistically ensure an annual risk of infection below 10-4), was assessed by evaluating the applicability of the Poisson lognormal (PLN) distribution in microbial risk assessment. PLN showed as good a fit to the observed data as to the negative binomial distribution. From the estimated PLN distributions for the source and finished water, the efficacy of the oocyst removal by the conventional water treatment process was estimated to follow lognormal distribution (median = 3.16 log10, 95% CI = 4.27-2.05 log10). The 365 consecutive negative results of daily monitoring for 180 L of finished water were found to be statistically equivalent to the annual risk of infection below 10-4. This research also suggested the possibility of applying a qualitative detection method, such as CC-PCR, as a routine monitoring method for the quantitative risk management.

Original languageEnglish
Pages (from-to)293-299
Number of pages7
JournalWater Science and Technology
Issue number1
Publication statusPublished - 2004


  • Cryptosporidium
  • Monitoring system
  • Poisson log-normal distribution
  • Risk assessment
  • Treatment efficacy

ASJC Scopus subject areas

  • Environmental Engineering
  • Water Science and Technology


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