AWWA WQTC69424

The Long Term 2 Enhanced Surface Water Treatment Rule (LT2) requires source water monitoring with samples analyzed by laboratories demonstrating competence with Method 1623: Cryptosporidium and Giardia in Water by Filtration/IMS/FA (EPA 2005). Method 1623 is a performance-based method and modifications may be incorporated to laboratory procedures after successful testing of the variation. Interferences during the immunomagnetic-separation (IMS) and microscopy steps of the method, such as suspended particles and associated constituents, may reduce the recovery of (oo)cysts. The subject studies suggest that these effects can be mitigated by the following: removing magnetized particles from the sample; rinsing the captured microbes with phosphate-buffered saline (PBS); and, dissociating microbes from the magnetic beads with heat rather than acid. Acceptable performance of these modifications has been demonstrated at the U.S. Environmental Protection Agency (USEPA), Technical Support Center in Cincinnati, Ohio with documented accuracy and precision, and results compared with more than 50 other LT2 laboratories. Includes 4 references, tables, figures.