AWWA JAW60490

Drinking water produced by conventional surface water treatment plants with typical levels of Cryptosporidium oocysts in source waters might put public health at risk. This study proves that oocysts that break through the treatment barriers could be alive and infectious under in vitro human cell culture conditions. Studies have shown that surface source waters and finished drinking water might be contaminated with Cryptosporidium oocysts. However none of the methods used in these studies, nor the currently approved US Environmental Protection Agency diagnostic techniques for compliance testing, are able to determine the public health significance of the results because those methods do not measure the infectivity of C. parvum. The study presented in this article showed that 90% of the finished water samples positive for Cryptosporidium occurred in filtered drinking water samples with low turbidities and that microbial indicators such as Bacillus, Clostridium, and phage were not associated with Cryptosporidium occurrence. Because none of the parameters analyzed could account for the occurrence of infectious Cryptosporidium in the treated water, it was concluded that conventional treatment plants are at risk for breakthrough of infectious oocysts. As a result of this study, the authors recommend that treatment should be improved using alternative disinfection techniques to preserve public health. Includes 36 references, tables, figures.