Ammoniacal nitrogen (NH3-N), is a measure for the amount of ammonia, a toxic pollutant often found in landfill leachate and in waste products, such as sewage, liquid manure and other liquid organic waste products. It can also be used as a measure of the health of water in natural bodies such as rivers or lakes, or in man made water reservoirs. The term is used widely in waste treatment and water purification systems.
Ammonia can directly poison humans and upset the equilibrium of water systems. The ammoniacal nitrogen levels can be lowered using a sequencing batch reactor.
The values of ammoniacal nitrogen in water or waste liquids are measured in milligram per liter and are used for specifying water treatment systems and facilities. The typical output of liquid manure from a dairy farm, after separation from the solids is 1600 mg NH3-N /L. Sewage treatment plants, receiving lower values, typically remove 80% and more of input ammonia and reach NH3-N values of 250 mg/L or less.
The ammonium nitrogen value is also used in the context of properly designed landfill systems, where the leachate is being pumped to the surface and treated before it enters the ground water, testing the quality of the water exiting the treatment system.
The term NH3-N removal is also commonly used in scientific publications as a short way to depict Ammonia in water, and not the measure of its quantity.
Structure and Basic Chemical Properties
Ammonium and ammonia forms of nitrogen compounds
Ammonia and Ammonium
Ammonia is highly soluble in water. Ammonia reacts with water (H2O) and forms the ionized form:
- NH3 + H2O ↔ NH4+ + OH-
The reaction is reversible. The hydroxide ion (OH-) plus NH4+ forms NH3 + H2O.
The percentage of ammonia increases with increasing alkalinity of dissolved ammonium in water. Ammonium ions are formed with increasing acidity of dissolved ammonia in water.
Ammonia is toxic to fish and humans. The toxicity is decreased with lower alkalinity and increases with higher alkalinity as ammonium is converted to ammonia.
Ammonia and mineral forms of Nitrogen
There are 3 basic forms of nitrogen:
- Mineral nitrogen
- Organic nitrogen
- Molecular nitrogen
The mineral forms of nitrogen are nitrate, nitrite and ammonium ions.
- Nitrate with the chemical structure of NO3-
- Nitrite with the chemical structure of NO2-
- Ammonium ions, with the chemical structure of NH4+ as mentioned above.
Ammoniums ions are nitrified and are converted by microorganisms into nitrate. Fish and humans are more tolerant of nitrate nitrogen than they are of ammonium nitrogen. In well aerated water, most of the mineral nitrogen is in the form of nitrate. See nitrogen cycle
Molecular nitrogen: Molecular nitrogen is the gas form of nitrogen in the atmosphere. The chemical structure for nitrogen gas is N2.
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- Manios, T; Stentiford, EI; Millner, PA (2002). "The removal of NH3-N from primary treated wastewater in subsurface reed beds using different substrates". Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering. 37 (3): 297–308. PMID 11929069.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
- Glossary of terms for water health measurement at the Sabine River Authority of Texas
- Wastewater Treatment to Minimize Nutrient Delivery from Dairy Farms to Receiving Waters a report for NOAA
- The terms NH3-N removal, and NH3-N fixation show up in over 1000 relevant results in web searches.
- Richard V. Tyson, Danielle D. Treadwell and Eric H. Simonne (2011). "Opportunities and Challenges to Sustainability in Aquaponic Systems". HortTechnology. 21 (1): 6–13.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>