Water Education - Water Quality

Nitrogen level: Pros and Cons Page 2

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Effect on warm water fish?

Contamination of water by nutrients has been a national concern for several decades. The earliest public interest was in lake and reservoir eutrophication, which produces unsightly scums of algae on the water surface and can occasionally result in fish kills. Beginning in the 1970s, additional concern focused on nutrients discharged to streams from sewage-treatment plants. Nutrients in treatment-plant effluent adversely affect aquatic life through direct toxicity and by removing oxygen from water during chemical transformations. The Water Pollution Control Act of 1972, later known as the Clean Water Act, mandated improvements in sewage-treatment technology, to be funded jointly by the Federal, State, and local governments. Twenty years later, the EPA reported that nutrients still were among the two leading causes of water-quality degradation in rivers, lakes, and estuaries throughout the Nation.

Also, one particular nutrient compound, nitrate, was reported to be the most prevalent contaminant in groundwater nationwide. The other nutrients of concern in water pollution are ammonia and phosphorus. The EPA has established a maximum contaminant level (MCL) of 10 mg/L (as nitrogen) for nitrate in drinking water. Excessive nitrate can result in the restriction of oxygen transport in the bloodstream. Infants under the age of 4 months lack the enzyme necessary to correct this condition. Fatalities from methemoglobinemia ("blue baby syndrome") occur infrequently and are most common in rural areas. Illness and death caused by methemoglobinemia are not always recognized; therefore, its occurrence might be underreported. Although one case in Colorado was attributed to infant formula made from public-supply water that had a nitrate concentration of 13.3 mg/L, most cases involve concentrations that are somewhat higher. In parts of Eastern Europe where groundwater is contaminated with 50-100 mg/L nitrate, pregnant women and children under 1 year of age are supplied with bottled water. Nitrogen, in the form of nitrate, nitrite, or ammonium, is a nutrient needed for plant growth.

About 78% of the air that we breathe is composed of nitrogen gas, and in some areas of the United States, particularly the northeast, certain forms of nitrogen are commonly deposited in acid rain. Although nitrogen is abundant naturally in the environment, it is also introduced through sewage and fertilizers. Chemical fertilizers or animal manure is commonly applied to crops to add nutrients. It may be difficult or expensive to retain on-site all nitrogen brought on to farms for feed or fertilizer and generated by animal manure. Unless specialized structures have been built on the farms, heavy rains can generate runoff containing these materials into nearby streams and lakes.

Wastewater-treatment facilities that do not specifically remove nitrogen can also lead to excess levels of nitrogen in surface or groundwater. Two of the major problems with excess levels of nitrogen in the environment are: Excess nitrogen can cause overstimulation of growth of aquatic plants and algae. Excessive growth of these organisms, in turn, can clog water intakes, use up dissolved oxygen as they decompose, and block light to deeper waters. This seriously affects the respiration of fish and aquatic invertebrates, leads to a decrease in animal and plant diversity, and affects our use of the water for fishing, swimming, and boating; Too much nitrate in drinking water can be harmful to young infants or young livestock.

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Read Next: Protect your Baby from Nitrates & Nitrites

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