AWWA JAW49886

In this study of a two-laboratory validation, the overall recovery of method 1622, an improvement over the Information Collection Rule (ICR) method for determining concentrations of Cryptosporidium oocysts and Giardia cysts in water, is about 35 percent with a 100-oocyst spike dosage. No nondetects were reported in the 32 natural samples analyzed, and the entire 10-L sample was anayzed on a single well slide. Elimination of subsample analysis in method 1622 reduces the possiblility of uneven oocyst recovery that can lead to over- or underestimation of total numbers in a sample. US Environmental Protection Agency's 13-laboratory round-robin collaborative trial of method 1622 showed that it is robust, with an overall recovery of 43 percent. Includes 32 references, tables, figure.