AWWA WQTC71358

This extended abstract presents a two year AWWARF-funded study to investigate the relative performance of all methods approved for use for the detection of coliforms and E. coli in drinking water in the U.S. and United Kingdom. This study investigated both the sensitivity and selectivity of each method. Many of the methods performed similarly, but those that utilize lactose fermentation for the detection of coliforms performed significantly worse than those that are based upon the detection of expression ß-D-galactosidase. The recovery of coliform organisms was significantly lower with methods using lactose-based media using naturally contaminated samples. The numbers of coliforms detected by methods using ß-D-galactosidase as the detection system was higher due to the number of slow lactose fermenting organisms present. However, while there were some differences in the genera detected, the differences were not significant. Methods utilizing ß-D-galactosidase detected more of the "common coliforms" such as Klebsiella, Citrobacter and Enterobacter than did lactose based methods as well as more recently described coliforms. Includes extended abstract only.