The Illinois EPA adopted new public water supply rules on July 25, 2019 that include modifications to analysis and reporting of new construction bacterial samples. Under the new rules, new construction samples must be reported as presence or absence of total coliform bacteria. This is a change from previous reporting requirements of no bacterial growth as measured by the membrane filtration method per Standard Methods 9222B. This change allows laboratories to adopt current presence/absence methods utilized for the analysis of routine compliance distribution samples for total coliform and e. coli. While the membrane filtration technique remains an approved method for both new construction and distribution samples, additional confirmation steps are now required when any bacteria is found to be present, leading to additional days of testing, increased turnaround time and cost. Effective immediately, Suburban Laboratories will no longer be using the membrane filter method.
Due to these rule changes, Suburban Laboratories has updated its policy to analyze all new construction samples by Colilert Presence/Absence method 9223B. This allows for more efficient analysis and faster reporting of results. It is understood that on some rare cases, a total count of coliform bacteria or e. coli is preferred. In these situations, Suburban Laboratories will analyze samples via method 9223B using Quanti-tray to obtain a quantifiable bacteria value. This procedure employs the same technique as in the presence/absence method, detects down to one (1) organism per 100 mL, and is an approved EPA method for drinking water samples. If you require quantification of your coliform samples, you must notify your project manager and specify this on all paperwork when delivering samples to the lab.