NITRATE (Nitrate Nitrogen) in Drinking Water

Nitrate Nitrogen. The concentration of nitrates is commonly expressed as N0₃^-. The term "nitrate nitrogen" is used to refer to the nitrogen present which is combined in the nitrate ion. This nomenclature is used to differentiate nitrate nitrogen from nitrogen in the form of ammonia (ammonia nitrogen), from nitrogen in the form of nitrite (nitrite nitrogen), etc. The concentrations are usually expressed in milligrams per liter of nitrogen.

Many ground waters contain small amounts of nitrate nitrogen. Concentrations range from 0.1 mg/l to 3 or 4 mg/l in most areas. Amounts as high as 100 mg/l have been found, however. Nitrates may occur in both shallow and deep well supplies, but they are most common in water from shallow wells. Nitrate nitrogen can result from the seepage of water through soil containing nitrate-bearing minerals. It may also occur as the result of using certain fertilizers in the soil; however, nitrates are one of the products of decomposition of animal and human wastes. Thus, the presence of nitrates in a water supply indicates possible pollution of the water.

Nitrate nitrogen has been much publicized in recent years in relations to the problem of "blue babies." In concentrations as low as 10 to 20 mg/1 nitrate nitrogen has caused illness and even death among infants under six months of age. If such water is used for supplemental or for complete bottle feeding, it may affect the ability of the blood to carry oxygen. This oxygen starvation is called methemoglobinemia, or more commonly, the "blue baby" condition. This serious illness in infants is caused because nitrate is converted to nitrite in the higher pH conditions existing in the stomachs and intestinal tracts of infants under six months of age. Nitrite interferes with the oxygen carrying capacity of a child's or baby animal's blood. This is an actue disease in that the symptons can develop rapidly. In most cases, health deteriorates rapidly over a period of days. Symptons include shortness of breath and blueness of skin.

In the process of decomposition, raw sewage undergoes a chemical change. Among the end products is nitrate nitrogen. When nitrate nitrogen occurs, it is considered evidence of pollution either from septic tank fields, cesspools or other sewage sources. Where a ground­water is known to contain little or no nitrate nitrogen naturally, the appearance of any significant increase is a probable indication of pollution. Because of these factors, well waters containing nitrate nitrogen should be checked periodically by local or state health authorities.

The best method for treatment of large nitrate nitrogen concentrations due to human or animal wastes is prevention. Wells should be properly located and constructed in order to prevent sewage contamination. Nitrates can be removed through distillation, deionization, or reverse osmosis. Even though about 95% of ionic nitrates can be removed by reverse osmosis, non­ionic forms of nitrogen are not rejected and pass through the membrane. In commercial and industrial water supplies nitrates do not usually present serious problems