Chlorine Injury and the Comparative Performance of Colisure™, Colilert™ and Coliquik™ for the Enumeration of Coliform Bacteria and E. coli in Drinking Water

Abstract

Several factors have stimulated interest in recently developed substrate specific media for the detection of coliform bacteria in water. This study compared the performance of Colisure (TM) (Millipore), ColiLert (TM) (Environetics) and ColiQuick (TM) (Hach) with accepted membrane filtration and MPN methodologies for the enumeration of total coliforms and E. coli in chlorinated water. The performance of all three media was compared, in MPN configuration, with LTB/MPN (confirmed) using a variety of drinking and source water samples, both with and without chlorination. The Cochran-Mantel-Haenszel test yielded statistical correlations between results obtained with each of the three new enzyme detection media and accepted reference methods for the detection of low numbers of total coliforms. Another series of tests compared the performance of Colisure with accepted methods (LTB/MPN confirmed with BGLB and EC-MUG) in the detection of total coliforms and E. coli in sewage-spiked samples simulating contaminated drinking water, using an USEPA/AWWA test protocol. The results demonstrated that Colisure detected these indicator bacteria with greater sensitivity than the accepted methods and that this difference increased between 24 and 28 hours of incubation. The results of this study collectively support the validity of the new enzyme detection method for the detection of low levels of coliform bacteria and E. coli in source water and contaminated drinking water.