ISO 9308-1:2014 PDF Download

ISO 9308-1:2014 is a standard that outlines a specific method for enumerating the presence of Escherichia coli (E. coli) and coliform bacteria in water samples. The method described in the standard utilizes membrane filtration, followed by the culturing of the filtered sample on a chromogenic coliform agar medium. This allows for the identification and quantification of the target organisms in the sample.

One crucial aspect addressed in this standard is the potential interference caused by background growth, which can compromise the accuracy of the enumeration of E. coli and coliform bacteria in certain types of water with low bacterial numbers. Therefore, ISO 9308-1:2014 specifies that this method is not suitable for surface waters or shallow well waters, where background growth may be more prevalent.

ISO 9308-1:2014 is particularly appropriate for waters that have a low bacterial background flora, resulting in less than 100 total colonies on chromogenic coliform agar. Examples of such waters include drinking water, disinfected pool water, and finished water from drinking water treatment plants.

It is worth noting that this standard also highlights that certain strains of E. coli that are negative for ß-D-glucuronidase, such as Escherichia coli O157, will not be detected as E. coli using this method. However, as these strains are positive for ß-D-galactosidase, they will still appear as coliform bacteria when using the chromogenic agar described in the standard.