Nitrates level in drinking water is recommended below 50 mg/L, specially for babies. Indeed, their digestive systems are immature, and thus more likely to allow the reduction of nitrate to nitrite. The nitrite in the digestive tract of babies can cause methenoglobinemia.
Nitrates can be removed by ion exchange using strong anionic resin in Cl- form.
Biological denitrification is used in municipal waste water treatment plant.