Nitrate (NO3-) is a dissolved form of nitrogen that is essential for plant growth but can be a serious water contaminant at elevated concentrations. High nitrate levels in drinking water can cause methemoglobinemia (blue baby syndrome) in infants.
Nitrate (NO3-) is a highly soluble inorganic ion formed through the oxidation of ammonia and organic nitrogen by nitrifying bacteria in soils and water. It is an essential plant nutrient, but excess nitrate in water bodies leads to eutrophication and poses direct health risks to humans. The primary sources of nitrate contamination in water include agricultural fertilizers, animal manure, septic system effluent, and atmospheric deposition from vehicle and industrial emissions. The EPA has set a maximum contaminant level of 10 mg/L for nitrate-nitrogen (NO3-N) in drinking water, primarily to protect infants from methemoglobinemia, a condition in which nitrate is converted to nitrite in the digestive system, interfering with the blood's ability to carry oxygen. Groundwater is particularly vulnerable to nitrate contamination because nitrate is highly mobile in soil and resistant to adsorption. Agricultural regions with intensive row crop production or concentrated animal feeding operations frequently have groundwater nitrate levels exceeding the MCL. Treatment options include ion exchange, reverse osmosis, biological denitrification, and blending with low-nitrate water sources.