Ammoniacal nitrogen
Encyclopedia
Ammoniacal nitrogen is a measure for the amount of ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

, a toxic pollutant
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

 often found in landfill
Landfill
A landfill site , is a site for the disposal of waste materials by burial and is the oldest form of waste treatment...

 leachate
Leachate
Leachate is any liquid that, in passing through matter, extracts solutes, suspended solids or any other component of the material through which it has passed....

 and in waste products, such as sewage
Sewage
Sewage is water-carried waste, in solution or suspension, that is intended to be removed from a community. Also known as wastewater, it is more than 99% water and is characterized by volume or rate of flow, physical condition, chemical constituents and the bacteriological organisms that it contains...

, liquid manure
Manure
Manure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil...

 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
Waste treatment
Waste treatment refers to the activities required to ensure that waste has the least practicable impact on the environment. In many countries various forms of waste treatment are required by law.-Solid waste treatment:...

 and water purification
Water purification
Water purification is the process of removing undesirable chemicals, materials, and biological contaminants from contaminated water. The goal is to produce water fit for a specific purpose...

 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
Sequencing batch reactor
Sequencing batch reactors or sequential batch reactors are industrial processing tanks for the treatment of wastewater. SBR reactors treat waste water such as sewage or output from anaerobic digesters or mechanical biological treatment facilities in batches...

.

The values of ammoniacal nitrogen in water or waste liquids are measured in milligram per liter
Litér
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 and are used for specifying water treatment systems and facilities. The typical output of liquid manure
Manure
Manure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil...

 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.

Ammonia and Ammonium

Ammonium is an ionized
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

 form of ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

.

The chemical structure for ammonium is NH4+.

The chemical structure for ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 is NH3.

Ammonia is highly soluble in water. Ammonium 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
Alkalinity
Alkalinity or AT measures the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate. The alkalinity is equal to the stoichiometric sum of the bases in solution...

 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 ammonia is converted to ammonium.

Ammonia and mineral forms of Nitrogen

There are 3 basic forms of nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

:
  • Mineral nitrogen
  • Organic nitrogen
  • Elemental nitrogen


Mineral nitrogen:

The mineral forms of nitrogen are nitrate, nitrite and ammonium ions.
  • Nitrate
    Nitrate
    The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

     with the chemical structure of NO3-
  • Nitrite
    Nitrite
    The nitrite ion has the chemical formula NO2−. The anion is symmetric with equal N-O bond lengths and a O-N-O bond angle of ca. 120°. On protonation the unstable weak acid nitrous acid is produced. Nitrite can be oxidised or reduced, with product somewhat dependent on the oxidizing/reducing agent...

     with the chemical structure of NO2-
  • Ammonium
    Ammonium
    The ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...

     ions, with the chemical structure of NH3 as mentioned above.


Ammonium
Ammonium
The ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...

s ions are nitrified and are converted by microorganisms into nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

. 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
Nitrogen cycle
The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out by both biological and non-biological processes. Important processes in the nitrogen cycle include fixation, mineralization, nitrification, and denitrification...



Organic nitrogen: The major organic forms of nitrogen include proteins, amino acids, DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

, and RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

.


Elemental nitrogen: Elemental nitrogen is the gas form of nitrogen in the atmosphere. The chemical structure for nitrogen gas is N2.
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