Nitrates
The presence of nitrate in a water analysis is a danger signal. Nitrate is an indication that the water supply may be contaminated with bacteria. Even small amounts of nitrate make the water supply suspect.
Many groundwaters contain small amounts of nitrate nitrogen. Concentrations range from 0.1 mg/l to 3 or 4 mg/l in many 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.

Therefore, the presence of nitrates in a water supply indicates possible pollution of the water. Large amounts of nitrate are dangerous to infants. Nitrate nitrogen has been much publicized in recent years in relation to the problem of "blue babies." In concentrations as low as 10 to 30 mg/l 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. Babies drinking high nitrate water develop a blue color of the skin because the blood has a decreased ability to carry oxygen. Continued drinking of the water will cause the baby to become ill, or may even result in death. Older children and adults are able to throw off the effects of nitrates in the blood. As serious as is this problem, it is not the major concern of public health officials. Rather, many feel it is a strong indicator of water pollution.
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 ground water 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 quantity of nitrate is reported by water analysis labs as nitrate (NO3) or as nitrogen (N). Some laboratories report nitrogen in ppm, (parts per million) and as nitrate in gpg, (grains per gallon). The USPHS acceptable limit for nitrate is 10 ppm reported as nitrogen (N).
Partial removal of nitrate can be accomplished by Reverse Osmosis (RO) filtration. Reverse osmosis may reduce the nitrates by about 40-90%. Complete removal of nitrate may be accomplished by deionization treatment. If the water supply is found to be contaminated, chlorination may be used to kill the bacteria. If the nitrate content cannot be reduced to an acceptable level, it is suggested that bottled water be used for drinking.