Nitrate (nitrate nitrogen) in drinking water
Interviewer: Can you provide a detailed explanation of what nitrate, specifically nitrate nitrogen, consists of, and talk about its presence in drinking water?
Could you delve into the specifics of Nitrate Nitrogen? Typically, the concentration of nitrates is denoted as NO3-. The term "nitrate nitrogen" is employed to describe the nitrogen that is integrated into the nitrate ion. This terminology helps to distinguish nitrate-nitrogen from other forms of nitrogen, such as ammonia nitrogen or nitrite-nitrogen. These concentrations are usually measured in milligrams per liter of nitrogen. Most groundwater sources contain minute quantities of nitrate nitrogen, with concentrations ranging from 0.1 mg/l to about 3 or 4 mg/l. However, in some areas, nitrate levels can reach up to 100 mg/l. While nitrates can be found in both shallow and deep water supplies, they are more prevalent in water from shallow wells. The presence of nitrate nitrogen can result from water percolating through soil rich in nitrate-bearing minerals or from the application of certain fertilizers. Moreover, nitrates are a byproduct of the decomposition of animal and human waste, suggesting that their presence in a water source may indicate potential contamination.
Nitrate nitrogen has garnered significant attention in recent years due to its association with "blue baby" syndrome. Even at concentrations as low as 10 to 20 mg/l, nitrate nitrogen can lead to illness or death in infants under six months of age if ingested through bottle feeding, as it can impair the blood’s oxygen-carrying capacity, leading to a condition known as methemoglobinemia, commonly referred to as "blue baby" syndrome. This condition arises because nitrate is converted to nitrite in the alkaline environment of an infant’s stomach and intestines, which in turn interferes with the blood’s oxygen-carrying ability. This is an acute condition that can cause rapid deterioration in health over several days, with symptoms including difficulty breathing and a bluish tint to the skin.
During the decomposition process, raw sewage undergoes a chemical transformation where soil bacteria convert various nitrogen forms into nitrates. Although this is beneficial for plants that absorb nitrogen in its nitrate form, nitrates are highly soluble and can easily leach through soil with water. Excessive rainfall or over-irrigation can cause nitrates to seep below the root zone of plants and infiltrate groundwater. The presence of nitrate-nitrogen is often indicative of pollution from septic tanks, cesspools, golf courses, parks, gardens, or natural sources of nitrogen. In groundwater naturally low in nitrate-nitrogen, any notable increase is likely a sign of contamination. Consequently, water authorities should periodically test well water for nitrate-nitrogen content.
What are the EPA’s drinking water regulations concerning nitrates?
In 1974, the Safe Drinking Water Act was passed by Congress, mandating the EPA to establish safe levels of contaminants in drinking water to prevent adverse health effects. The regulatory standard for nitrates is set at 1mg/L or 1 ppm. However, individual states may enforce stricter nitrate levels than those set by the EPA. The EPA also requires that all community water systems provide an annual water quality report to their customers. Despite this, there is still uncertainty regarding the relationship between nitrate levels in drinking water and health risks, including the amount ingested, duration of exposure, and potential risks. It is highly recommended to be vigilant about the quality of your drinking water and to contact your water utility to inquire about nitrate levels. If you rely on a private well, you will need to pay for testing, as private wells are not currently regulated.
The most effective strategy to prevent high nitrate nitrogen concentrations from human or animal waste is through prevention. Wells should be appropriately situated and constructed to avoid sewage contamination. Nitrates can be removed through processes such as distillation, deionization, or reverse osmosis. Although reverse osmosis can eliminate about 95% of ionic nitrates, non-ionic nitrogen forms can pass through the membrane. In commercial and industrial settings, nitrates typically do not pose serious issues.
Since nitrate in water is colorless, odorless, and tasteless, it is undetectable without testing. It is therefore crucial to be aware of the contaminants in your drinking water and to take appropriate action. Access to pure drinking water should be a right, not a privilege, yet pollution is increasingly hindering access to clean water. The use of filtration systems is advised to safeguard your health and to purify your drinking water source, whether from a well or the city supply. Systems like reverse osmosis can remove contaminants, discoloration, odors, heavy metals, bacteria, and more. Given the prevalence of outdated pipes in water transportation, filtration is now recommended in every home. It is always wisest to take necessary precautions to ensure a clean and healthy water supply for your family, both present and future generations.