Nitrates/Nitrites

Nitrates/Nitrites: From Water Technology Magazine, Volume 31, Issue 5 - May 2008

What they are:
Symbols:
Nitrate = NO3-

Nitrite = NO2-

Nitrate, with a single negative charge, is an ion (or salt) of nitric acid (HNO3) or other organic or inorganic substances, such as potassium nitrate (KNO3). Nitrite, also with a single negative charge, is an ion (or salt) of nitrous acid (HNO2) or other substances.

Properties:

Nitrate is colorless, odorless, tasteless, very stable and easily dissolves in water. It moves with water and can migrate for miles from its source.

Nitrite is unstable and quickly reacts with other compounds.

Conversions:
Levels of nitrate can be expressed in either of two ways: “nitrate as nitrogen” (symbol: NO3-N) or simply as nitrate (NO3). To convert NO3-N to NO3 in parts per million (ppm, or mg/L), multiply NO3-N by 4.42.

In ion exchange treatment, to convert NO3 to the calcium carbonate (CaCO3) equivalent in ppm, multiply the NO3 value by 0.81.

Occurrence/health effects:
Nitrates occur:
Naturally in water at low levels. Plants use nitrates as a nutrient. Most nitrates consumed by humans come from dietary raw or cooked vegetables, with few known health effects.

In high levels when microorganisms break down fertilizers, animal waste, wastewater or septic seepage, urban drainage or decaying plants. Due to agricultural runoff or animal feedlots, rural waters may be high in nitrates.

Health effects:
Water high in nitrates that is ingested by infants, pregnant women, adults with low stomach acidity or people with a certain enzyme deficiency can cause methemoglobinemia, or “blue baby syndrome,” as the ingested nitrates are converted to nitrites in the body. This reduces the oxygen-carrying capacity of the blood, and severe cases result in brain damage or death.

Prolonged intake of high nitrates can result in gastric distress in humans and has been shown to cause cancer in test animals.


Regulation:
US Environmental Protection Agency (EPA) (primary) maximum contaminant levels are:
Nitrate: NO3-N = 10 mg/L, or NO3 = 45 mg/L

Nitrite (as nitrogen) = 1 mg/L

Water treatment:
Ion exchange, reverse osmosis, distillation, blending (dilution).

Ion exchange media for nitrates/nitrites can include standard strong base anion exchange resins, or nitrate-selective resins.
Sources: US EPA, Colorado State Cooperative Extension, Minnesota Department of Health, The Nitrate Elimination Co., Inc., Dave Bauman.