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Environmental Health Division
Sulfate In Well Water
Sulfate occurs naturally in most of Minnesota’s groundwater. Higher levels of sulfate are common in the western part of the state. At high levels, sulfate can give water a bitter or medicinal taste and can have laxative effects.
You can find out the level of sulfate in your water by having the water tested at a laboratory.
Health risks for humans
People who are not used to drinking water with high sulfate can get diarrhea and dehydration from drinking the water. Infants are often more sensitive to sulfate than adults. To be safe, only use water with a sulfate level lower than 500 milligrams per liter (mg/L) to make infant formula. Older children and adults may get used to high sulfate levels after a few days.
Health risks for animals
Animals are also sensitive to high levels of sulfate. In young animals, high levels may be associated with severe, chronic diarrhea and even death. Animals tend to get used to sulfate over time. Diluting water high in sulfate with water low in sulfate can help avoid problems of diarrhea and dehydration in young animals and animals not used to drinking high sulfate water. Contact a veterinarian or your county office of the Minnesota Extension Service for more information.
Other problems Sulfate can cause
Sulfate levels above 250 mg/L may make the water taste bitter or like medicine. High sulfate levels may also corrode plumbing, particularly copper piping. In areas with high sulfate levels, plumbing materials more resistant to corrosion, such as plastic pipe, are commonly used.
Ways to treat Sulfate
Four types of treatment systems will remove sulfate from drinking water:
- Reverse osmosis pushes water through a membrane with tiny pores. The membrane stops many contaminants, including sulfate, while allowing water to pass through. Reverse osmosis usually removes between 93 and 99 percent of the sulfate in drinking water, depending on the type of treatment unit.
- Distillation is a process that boils water, making steam. The steam rises and leaves contaminants, such as sulfate behind. With proper operation, distillation units can remove nearly 100 percent of sulfate.
- Anion exchange is the most common method of removing large quantities of sulfate from water for commercial, livestock, and public supplies. It is not commonly used for individual household water treatment. It is a process that replaces negatively charged ions (such as sulfate) with sodium chloride or potassium chloride (salts).
- Adsorptive media filtration has a charged media bed that can force ions of the opposite charge (such as sulfate) to be pulled out of the water and attach to the media.
Learn more about these treatment options at the Home Water Treatment webpage.
A few other things to note about home water treatment for sulfate:
- If both a water softener and a sulfate removal system are used, the water softener is usually placed before the sulfate removal system.
- Water softeners, carbon filters, and sediment filters do not remove sulfate.
- Any water treatment system requires proper operation and maintenance to ensure that it continues to function properly. It is important to follow the recommendations of the manufacturer and installer for the maintenance of the water treatment system.
How Sulfate gets into groundwater
As water moves through soil and rock formations that contain sulfate minerals, some of the sulfate dissolves into the groundwater. Minerals that contain sulfate include magnesium sulfate (Epsom salt), sodium sulfate (Glauber’s salt), and calcium sulfate (gypsum).
Sulfate in Minnesota groundwater
The level of sulfate in most groundwater in Minnesota is low, less than 250 milligrams per liter (mg/L). High levels of sulfate (sometimes above 1000 mg/L) are more common in the southwestern areas of Minnesota and along the western boundary of the state. High levels of sulfate also occur, though less commonly, in some wells in the northeastern and southeastern parts of the state.
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Should I test my well water for anything besides Sulfate?
Yes. Both natural sources and human activities can contaminate well water and cause short-term or long-term health effects. Testing your well water is the only way to detect most of the common contaminants in Minnesota groundwater; you cannot taste, see, or smell most contaminants. Minnesota Department of Health recommends testing for:
- Coliform bacteria every year and any time the water changes in taste, odor, or appearance. Coliform bacteria can indicate that disease-causing microorganisms may be in your water.
See Bacterial Safety of Well Water.
- Nitrate every other year. Bottle-fed infants under six months old are at the highest risk of being affected by levels of nitrate higher than 10 milligrams per liter in drinking water.
See Nitrate in Well Water.
- Arsenic at least once. About 40 percent of wells in Minnesota have arsenic in the water. Drinking water with arsenic in it for a long time can contribute to reduced intelligence in children and increased risks of cancer, diabetes, heart disease, and skin problems.
See Arsenic in Well Water.
- Lead at least once. The well and water system may have parts that have lead in them, and that lead can get into drinking water. Lead can damage the brain, kidneys, and nervous system. Lead can also slow development or cause learning, behavior, and hearing problems.
See Lead in Well Water Systems.
- Manganese before a baby drinks the water. High levels of manganese can cause problems with memory, attention, and motor skills. It can also cause learning and behavior problems in infants and children.
See Manganese in Drinking Water.
Other contaminants sometimes occur in private water systems, but less often than the contaminants listed above. Consider testing for:
- Volatile organic chemicals if the well is near fuel tanks or a commercial or industrial area.
- Agricultural chemicals commonly used in the area if the well is shallow and is near cropped fields or handling areas for agricultural chemicals or is in an area of geologic sensitivity (such as fractured limestone).
- Fluoride if children or teenagers drink the water.
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