SABATTUS — Town officials plan to add a small dose of chlorine to the water supply after a trace of coliform bacteria was detected during testing in July.

“The bacteria is harmless but used as an indicator,” according to a notice sent to residents Tuesday. “The water district will introduce a low dosage of chlorine to the distribution system as a precautionary measure. You may experience a chlorine taste that will dissipate within a couple weeks. Sorry for the inconvenience but the water district strives for clean and safe water.”

The same notice was sent in July after the bacteria was first detected.

The Centers for Disease Control and Prevention’s regulations assert coliform bacteria must not be present at all in drinking water.

According to the Maine Division of Public Health Systems, coliform bacteria is a large group of bacteria found in soil, on plants and in surface water and lives in the intestines of humans and other animals.

“Coliforms are not harmful themselves, but when present in drinking water, disease-causing microorganisms such as bacteria, viruses, and parasites may have gotten into the water supply by the same route as the coliforms,” according to a Maine DPHS fact sheet. “The Maine Health and Environmental Testing Laboratory tests for coliforms as an indicator for possible contamination.”