What is the MCL for coliform if taking 40 or more samples per month?

The maximum contaminant level (MCL) for total coliform bacteria in drinking water is established by the Environmental Protection Agency (EPA) to ensure safe and clean drinking water. When the requirement is to take 40 or more samples per month, the standard allows for a specific percentage of those samples to test positive for coliform bacteria.

In this case, if you are taking 40 or more samples per month, the acceptable limit for positive coliform samples is set at no more than 5% of those samples. This means that out of 40 samples, a maximum of 2 positive results would be allowable to remain in compliance with the regulations. This limit is critical for protecting public health and indicates that while coliform bacteria may be present, it should be at a very low level for the water to be considered safe for consumption.

Understanding the MCL for coliform is essential for water operators, as it guides the monitoring and testing protocols necessary to ensure water quality and safety for the community.