Methods for the recovery, isolation and detection of Cryptosporidium oocysts in wastewaters

This correspondence describes the successful development of methods for the recovery, isolation and detection of Cryptosporidium oocysts in wastewater and biosolids. Wastewater from one plant was used to optimize methods in raw influent as well as primary, secondary and tertiary effluents. Raw influents and primary effluents were concentrated using centrifugation followed by isolation of Cryptosporidium oocysts using immunomagnetic separation (IMS) and detection of recovered organisms using epifluorescence microscopy. Mean oocyst recovery in raw influent was 29.2 ± 12.8% and 38.8 ± 27.9% in primary effluent at three sample volumes tested. Secondary and tertiary effluents were analyzed using a modified Method 1622 resulting in mean oocyst recoveries of 53.0 ± 19.2% and 67.8 ± 4.4%, respectively. In biosolids with approximately 10% total solids, mean oocyst recovery was 43.9 ± 10.1% using IMS with a 5 g (wet weight) sample size. Due to the variability in these matrices, an internal microbiological standard was incorporated to serve as a tool for method performance.