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Ag Water Stewardship: Take action to test well and tap water for harmful coliform bacteria, nitrates and more.

Warren Formo

March 15, 2024

4 Min Read
hands around a glass of water
PUT WATER TO TEST: Residents are encouraged to have their well water and tap water tested to ensure that it is safe to drink. Oleg Elkov/Getty Images

We all know the importance of good, safe drinking water. A few months ago, this column was devoted to the importance of private well testing as one part of providing safe drinking water for your family. This month, I will continue that conversation in more detail.

Unlike customers of municipal water providers, private well owners have the responsibility to test and treat their drinking water. The Minnesota Department of Health offers helpful guidance on testing and appropriate responses through a series of fact sheets available on the MDH website.

Back in the old days, most people took the safety of well water for granted. Over time, the list of potentially harmful contaminants has grown as more has been learned about human health and water.

In recent months, attention to private wells has become a high-profile issue, especially in southeast Minnesota’s karst region.

More than nitrates

The MDH currently recommends having your well tested for coliform bacteria and nitrates annually, and arsenic, manganese and lead at least once.

Arsenic is a known carcinogen. The U.S. EPA drinking water standard is 10 micrograms per liter, but as it is a carcinogen, the EPA has set a goal of zero.

In addition to cancer, arsenic can contribute to a long list of health problems. According to the MDH, “Health impacts of arsenic may not occur right away and can develop after many years, especially if you are in contact with arsenic at a low level over a long time.”

Arsenic is detected in about half of the wells in Minnesota and found at levels above 10 parts per billion in about 10% of wells.

Manganese occurs naturally in the soil and rocks across Minnesota. There is no drinking water standard for manganese, but the MDH has developed guidance values of 100 ppb for consumption by infants and 300 ppb for those older than 1. Manganese can cause staining and give water a bad odor or taste. Health effects of manganese include memory loss, attention and motor skill deficits in children and adults, and learning and behavior problems in infants.

The nitrate drinking water standard of 10 milligrams per liter is intended to be protective of infants consuming formula. Nitrates are found above the drinking water standard in about 3% of wells statewide and in about 10% in areas of rapid water infiltration, including the karst region.

Methemoglobinemia, also known as blue baby syndrome, has been associated with the consumption of water with high nitrate levels by infants. The ability to metabolize nitrates is acquired during the infant’s first few months. Some studies suggest an increased risk of cancer due to nitrate exposure, but according to the MDH, “there is not yet scientific consensus on this question.”

Bacteria in drinking water can cause stomach illnesses including vomiting and diarrhea. Testing is recommended to determine whether coliform bacteria are present or not. If they are, disinfection with chlorine is usually effective.

Lead in drinking water is not a well issue but can be found in older homes with plumbing fixtures or service lines that contain lead. The health effects of lead are numerous, and there is no safe level of lead — period. Since the source of lead would most likely be coming into or inside the house, testing should be done at the tap.

Call to action

So here is my call to action. If you have not already done so, get your well and tap water tested!

I want to emphasize the importance of testing both directly from the well and at the tap, except for lead, in which case you only need to test at the tap. Testing at the well is useful, as this information is helpful in deciding on treatment, but the most important measure is knowing the safety of the water you and your family actually consume. Testing both will also confirm that your treatment system is working.

I close with a thank you to those who have already tested your drinking water and taken appropriate action. You can be confident in the safety of your drinking water. And thank you in advance to those of you who take action now! To learn more about well testing, approved laboratories, and more, check out the MDH website.

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Healthy Living

About the Author(s)

Warren Formo

Warren Formo is executive director of the Minnesota Agricultural Water Resource Center.

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