A four-year systematic study of microbial water quality in the surface waters of central Arizona was performed. The objectives of this study were to investigate the occurrence of microbial pathogens and indicators in the waters. A total of 192 water samples from five sites were analyzed for Cryptosporidium, Giardia, and various microbial and physical indicators. Ten percent (16/162) of the samples collected using EnviroChek filters were positive for Cryptosporidium oocysts, whereas no oocysts (<1 in 5 L) were detected in the grab samples (0/30). Giardia cysts were detected in 10% (3/30) of the grab samples and in 27% (44/162) samples collected using EnviroChek filters. Mean concentrations of oocysts in the source waters at the treatment plants were lower than the Bin 1 category of the USEPA Long Term 2 Enhanced Surface Water Treatment Rule; therefore no additional treatment is required by the plants. The annual risks of infection from Cryptosporidium met the annual acceptable risk of 10−4 at all sampling sites, whereas the risks of Giardia infection at the Verde River and the Salt River were 5.70E-04 and 2.66E-04, respectively.
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Research Article|
January 01 2008
Long-term study of Cryptosporidium and Giardia occurrence and quantitative microbial risk assessment in surface waters of Arizona in the USA
Hodon Ryu;
Hodon Ryu
1Arizona State University, National Science Foundation Water Quality Center, Department of Civil and Environmental Engineering, ECG 252, Tempe, AZ 85287-5306, USA
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Morteza Abbaszadegan
1Arizona State University, National Science Foundation Water Quality Center, Department of Civil and Environmental Engineering, ECG 252, Tempe, AZ 85287-5306, USA
Tel.: +1 480 965 3868 Fax: +1 480 965 0557; E-mail: [email protected]
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J Water Health (2008) 6 (2): 263–273.
Article history
Received:
December 27 2006
Accepted:
April 07 2007
Citation
Hodon Ryu, Morteza Abbaszadegan; Long-term study of Cryptosporidium and Giardia occurrence and quantitative microbial risk assessment in surface waters of Arizona in the USA. J Water Health 1 June 2008; 6 (2): 263–273. doi: https://doi.org/10.2166/wh.2008.030
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