Occurrence of Cryptosporidium in Source Waters and Its Quantitative Microbial Risk Assessment

Abstract

The occurrence of Cryptosporidium in raw water and its quantitative microbial risk assessment (QMRA) were performed based on the results of water quality surveys conducted by the Ministry of Health, Labor and Welfare, Japan for water supply works nationwide. For 95% of all tested source waters, it is estimated that the target infection risks and disease loads can be achieved with the removal rate of 3 to 4 logs obtained by general coagulation sedimentation-rapid filtration and chlorination. Due to there is no margin for dangerous events such as an increase in the concentration of Cryptosporidium in raw water, and we emphasized necessary to implement additional treatment such as UV irradiation, or monitoring of Cryptosporidium, high frequency.