ISO 9308-2:1990

This part of ISO 9308 specifies a method for the detection and enumeration in water of coliform organisms, thermotolerant coliform organisms and presumptive Escherichia coli (presumptive E. coli) by culture in a liquid medium in multiple tubes and calculation of their most probable numbers in the sample.

This method can be applied to all types of water, including those containing an appreciable amount of suspended matter.

The choice of tests used in the detection and confirmation of the coliform group of organisms, including E. coli, can be regarded as part of a continuous sequence. The extent of confirmation with a particular sample depends partly on the nature of the water and partly on the reasons for the examination. In practice, the detection in water of presumptive E. coli as defined in 3.3 of this part of ISO 9308, usually provides an indication of recent faecal pollution.