AWWA WQTC64116

Despite the improved Cryptosporidium recoveries (relative to previous methods) that have been obtained using U.S. Environmental Protection Agency method 1622/23, processing large volumes of raw and treated water has remained a laborious, unreliable and costly task. Emelko and Reilly (2002) demonstrated increasing the number of counts in a sample can be integral to reducing the uncertainty in concentration and log removal estimates. One strategy substantially reducing uncertainty associated with the concentration and enumeration of C. parvum is to increase processed volume (with increased replication or improved analytical methods) so that at least several oocysts (at least ten or more as opposed to one or none) are observed. This paper demonstrates a modified form of previously reported membrane filtration methods for Cryptosporidium and oocyst-sized surrogate enumeration. A critical and unique feature of this modified method is that large volumes of water can be processed, concentrated, and enumerated. Preliminary investigations utilizing deionized water, groundwater, and treated surface water samples of up to 2000L (and all with turbidities <0.3 NTU) have demonstrated C. parvum recoveries of approximately 45-50% and oocyst-sized microsphere recoveries of 70-90%. This approach provides a cost-effective alternative method for conducting performance demonstrations and seeding experiments. Includes 27 references, tables, figures.