Water Testing Display

Common Indicators of Health Risks in Your CT Well Water

Indicators of Well Water Contamination RiskNitrate-nitrogen and coliform bacteria are two common indicators of drinking water contamination in CT and tests for these are the most common tests that are run on private wells.

Analysis for coliform bacteria and nitrate is relatively simple and inexpensive and elevated levels of either can indicate contamination of the well.


Nitrate occurs in the soil, crop residues, human or animal wastes, some industrial wastes, and nitrogen fertilizers. All are possible sources of nitrate, which is soluble and moves easily with surface and groundwater.

Although nitrate itself is not harmful to humans, certain bacteria change nitrate to nitrite in the digestive tract. Infants under six months of age have weak stomach acids that allow those nitrate-reducing bacteria to grow and produce nitrite.

When nitrite is absorbed into the blood, it reduces the ability of hemoglobin (red oxygen-carrying blood pigment) to carry oxygen from the lungs to the rest of the body. This change in the blood is described as a change from hemoglobin to methemoglobin.

Thus, some infants under six months of age are especially susceptible to excess nitrate in water and may develop a condition called¬†methemoglobinemia, or “blue-baby” syndrome. Methemoglobinemia produces a bluish color around the lips, spreads to the fingers, toes, and face, and in extreme cases, covers the entire body. In severe cases, the infant is unable to obtain sufficient oxygen and may die. Unfortunately, methemoglobinemia remains a potential threat for infants in Connecticut.

The USEPA Primary Drinking Water Standard for nitrate-nitrogen is 10 parts per million (ppm) or 10 milligrams per liter (mg/L). The ppm measurement is equivalent to milligrams per liter (mg/L). This standard was established to protect infants because they are the population most sensitive to nitrate.

Coliform bacteria

Coliform bacteria are prevalent in the colon and feces of warm-blooded animals and can be carried into CT water supplies by wastewater. Although most of the 15 species of coliform bacteria do not by themselves cause disease, they do indicate that other disease-causing bacteria and viruses may also be in the water supply. The coliform test is commonly used as an indicator of water contamination.

The source of bacteria is usually in the immediate vicinity of the well itself. It may result from improperly constructed or maintained septic systems, feedlots, or waste, or it may have become established in household plumbing during maintenance.

Because the test involves culturing, or growing, bacteria, it is extremely important that the water sample be analyzed within 30 hours and should be protected from sunlight and temperature extremes.


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