Information on related products can be found on the following pages:

Point of Entry (POE) Nitrate Filters

Reverse Osmosis Systems

Distillation Systems

Sources of Nitrates

Nitrate (NO₃) is a naturally occurring form of nitrogen found in soil. Nitrogen is essential to all life. Most crop plants require large quantities to sustain high yields.

The formation of nitrates is an integral part of the nitrogen cycle in our environment. In moderate amounts, nitrate is a harmless constituent of food and water. Plants use nitrates from the soil to satisfy nutrient requirements and may accumulate nitrate in their leaves and stems. Due to its high mobility, nitrate also can leach into groundwater. If people or animals drink water high in nitrate, it may cause methemoglobinemia, an illness found especially in infants.

Nitrates form when microorganisms break down fertilizers, decaying plants, manures or other organic residues. Usually plants take up these nitrates, but sometimes rain or irrigation water can leach them into groundwater. Although nitrate occurs naturally in some groundwater, in most cases higher levels are thought to result from human activities. Common sources of nitrate include:

• fertilizers and manure,
• animal feedlots,
• municipal wastewater and sludge,
• septic systems, and
• N-fixation from atmosphere by legumes, bacteria and lightning.

Health Effects of Nitrates

High nitrate levels in water can cause methemoglobinemia or blue baby syndrome, a condition found especially in infants under six months. The stomach acid of an infant is not as strong as in older children and adults. This causes an increase in bacteria that can readily convert nitrate to nitrite (NO₂). Do not let infants drink water that exceeds 10 mg/l NO₃-N. This includes formula preparation.

Nitrite is absorbed in the blood, and hemoglobin (the oxygen-carrying component of blood) is converted to methemoglobin. Methemoglobin does not carry oxygen efficiently. This results in a reduced oxygen supply to vital tissues such as the brain. Methemoglobin in infant blood cannot change back to hemoglobin, which normally occurs in adults. Severe methemoglobinemia can result in brain damage and death.

Healthy adults can consume fairly large amounts of nitrate with few known health effects. In fact, most of the nitrate we consume is from our diets, particularly from raw or cooked vegetables. This nitrate is readily absorbed and excreted in the urine. However, prolonged intake of high levels of nitrate are linked to gastric problems due to the formations of nitrosamines. N-nitrosamine compounds have been shown to cause cancer in test animals. Studies of people exposed to high levels of nitrate or nitrite have not provided convincing evidence of an increased risk of cancer.

Testing

Nitrate is a tasteless, colorless and odorless compound that you cannot detect unless your water is chemically analyzed. If you drink water from a private well, get a qualified laboratory to test it yearly. The local health department usually can supply the name of an approved testing laboratory in your area.

Sample water for nitrate testing at the well site or at a tap inside the house. Place samples in clean, 4- to 16-ounce plastic containers. Send the sample to a laboratory immediately. Refrigerating it will help keep it intact until it reaches a laboratory. Do not freeze it.

Laboratory results will be compared to the MCL, and recommendations for treatment should be considered if nitrate levels exceed 10 mg/l NO₃-N. Be aware that nitrate levels in groundwater may vary seasonally. If your water tests high or borderline high, retest your water every three to six months.

Interpreting Test Results

Public drinking water standards established by EPA fall into two categories -- Secondary Standards and Primary Standards. Secondary Standards are based on aesthetic factors such as taste, odor, color, corrosivity, foaming, and staining properties of water that may affect the suitability of a water supply for drinking and other domestic uses. Primary Standards are based on health considerations and are designed to protect human health. The EPA has established an enforceable Primary Standard for nitrates in public drinking water supplies.

Nitrate values are commonly reported as either nitrate (NO₃) or as nitrate-nitrogen (NO₃-N). The maximum contaminant level (MCL) in drinking water as nitrate (NO₃) is 45 mg/l, whereas the MCL as NO₃-N is 10 mg/l.

The MCL is the highest level of NO₃ or NO₃-N that is allowable in public drinking water supplies by the U.S. Environmental Protection Agency (EPA). These figures also may be reported in ppm (parts per million), which is equivalent to mg/l. Be sure you know which value is reported for your water sample.

Options

Nitrate/nitrite can be removed from water supplies by the following treatment processes: ion exchange, reverse osmosis, and distillation.

• Ion-exchange takes another substance, such as chloride, and trades places with nitrate. An ion exchange unit is filled with special resin beads that are charged with chloride. As water passes over the beads, the resin takes up nitrate in exchange for chloride. As more water passes over the resin, all the chloride is exchanged for nitrate. The resin is recharged by backwashing with sodium chloride solution. The backwash solution, which is high in nitrate, must be properly disposed of.
• Reverse osmosis forces water under pressure through a membrane that filters out minerals and nitrate. One-half to two-thirds of the water remains behind the membrane as rejected water. Higher-yield systems use water pressures of 150 psi.
• Distillation boils the water, catches the resulting steam, and condenses the steam on a cold surface (a condenser). Nitrates and other minerals remain behind in the boiling tank.

Summary

Nitrate in drinking water can be a problem, especially for infants. A water test is the only way to determine whether the nitrate-nitrogen concentration is under the acceptable standard of 10 mg/L. Proper well location and construction are key practices to avoiding nitrate contamination of drinking water. Management practices to reduce the risk of contamination from applied fertilizers and manure help keep the water supply safe.

If drinking water exceeds the acceptable nitrate-nitrogen standard, the choices are to use an alternate water supply or treat the water. An alternate supply may be bottled water for drinking, especially for infant formula, or a new well in a different location or aquifer. Water treatment options are distillation, reverse osmosis, or ion exchange.