Ammonia and Water quality

Ammonia (NH3) is a colorless gas with a strong pungent odor. It is easily liquefied and solidified and is very soluble in water. One volume of water will dissolve 1,300 volumes of NH 3. Ammonia will react with water to form a weak base.

Methodology: An ammonia ion-specific electrode can be used with a computer aided titrimeter (CAT). However, Ion Chromatography is a more accurate and efficient method for anion identification. Ammonia concentration is usually reported as total (NH3/NH4-N) ammonia nitrogen.

Environmental Impact: About three-fourths of the ammonia produced in the United States is used in fertilizers, either as the compound itself or as ammonium salts such as sulfate and nitrate. Large quantities of ammonia are used in the production of nitric acid, urea and nitrogen compounds. It is also used in the production of ice and in refrigerating plants. "Household ammonia" is an aqueous solution of ammonia. It is used to remove carbonate from hard water. Since ammonia is a decomposition product from urea and protein, it is found in domestic wastewater. Aquatic life and fish can also contribute to ammonia levels in a stream.

NH3 is the principal form of toxic ammonia. It has been reported to be toxic to fresh water organisms at concentrations ranging from 0.53 to 22.8 mg/L. Toxic levels are both pH and temperature dependent; toxicity increases as pH decreases and as temperature decreases. Plants are more tolerant of ammonia than animals, and invertebrates are more tolerant than fish. Hatching and growth rates of fishes may be affected while structural development changes may occur in tissues of gills, liver, and kidneys may also occur. Toxic concentrations of ammonia in humans may cause loss of equilibrium, convulsions, coma, and death.

Criteria: The un-ionized form of ammonia (NH3) should not exceed 0.05 mg/L in order to protect aquatic organisms. This is calculated from total ammonia using temperature and pH in a formula.

2007 Arizona Board of Regents for The University of Arizona