ABSTRACT
The main source of nitrogen is the air. When in water media, nitrogen can be divided into suspended and dissolved organic (from a living material) and inorganic (ammonia, nitrate, and nitrite) compounds. There is a huge variety of nitrogen organic compounds in the environment. Organic nitrogen (ON) can also enter systems as bodily wastes, discarded food material, or as components of cleaning agents. The nitrogen cycle further comprises the transformation of ON in inorganic compounds. The conversion of ON in ammonia (NH3) and then in ammonium ion (NH4+) indicates the onset of oxidation process, which will produce nitrite (NO2−) and then nitrate (NO3−), called the nitrication process. The importance of understanding the presence, and quantifying nitrogen in its various forms in water, refers to the consumption of dissolved oxygen required during the nitrication process and, mainly, in the proliferation of microalgae, whose nitrogen is a vital element in its growth.
