Environmental Services Program
Escherichia coli Analysis
Water Quality Monitoring Section staff use the IDEXX Colilert® and Quanti-Tray® system for detection and enumeration of Escherichia coli (E. coli) and total coliforms. The method can be applied to ambient fresh waters, drinking waters and wastewaters. The Colilert® method is not intended for use with marine waters.
The EPA-approved Colilert® method is based on Defined Substrate Technology®. The product utilizes nutrient indicators that produce color and/or fluoresce when metabolized by total coliforms and E. coli. After the reagent is added to the sample and incubated, it can detect these bacteria at 1 MPN (most probable number) per 100mL within 24 hours with as many as 2 million heterotrophic bacteria per 100mL present.