Nitrification

Nitrification

Nitrification
Nitrification is a two-step process involving ammonium oxidation and nitrite oxidation.

Ammonium Oxidation
This is done by some aerobes called ammonia oxidisers like Nitrosomonas, Nitrosococcus, Nitrosolobus, etc.

The ammonia released during ammonification is oxidised to form nitrites. Nitrite is a transient compound and is not usually taken up by plants or microbes. Nitrite ions are toxic and they are readily oxidised to form nitrates which are the assimilable form of nitrogen.

The ammonia oxidising bacteria are chemoautotrophs (obligate) which occur as rods, ellipsoids, spirilla and cocci. They are non-spore forming organisms. Major species of Nitrosomonas are N. eurospora. They are gram-negative motile organisms and their optimum growth temperature is 30°C at 7.5-8 pH.

Nitrite Oxidation
The produced nitrite is immediately oxidised to assimilable nitrate and the organisms involved are Nitrobacter and Nitrospira sp. The organisms are aerobic, gram-negative rods, spherical or spiral shaped. Their optimum temperature is 28°C with a pH requirement of 5.8-8.5.

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