What is the required volume of a sample for coliform compliance?

The required volume of a sample for coliform compliance is 100 mL. This volume is specifically set by regulatory standards to ensure that the sample is representative of the water quality and provides sufficient volume for accurate laboratory analysis. In the case of testing for coliform bacteria, a 100 mL sample is a standard volume that balances the need for statistical significance with practical considerations of sample collection and testing.

Using a lesser volume might not provide enough bacteria to detect in cases where they are present in low concentrations. Conversely, using too large a volume could complicate the testing process and may not yield proportionately better detection results, as the presence of coliform bacteria can vary widely in smaller water samples. Therefore, the selection of 100 mL is based on established scientific protocols following guidelines from organizations such as the U.S. Environmental Protection Agency (EPA) and the American Public Health Association (APHA).