Ammonia and ammonium are cationic chemical compounds that are formed from nitrogen and hydrogen. They are widespread contaminants in water as their industrial use is very common, especially in the creation of fertilizers.
What is ammonia
Composed of three hydrogen atoms and one nitrogen atom, ammonia is a chemical compound (NH3) which, at room temperature, is in a colorless gaseous state, but very irritating and with a pungent smell. When it comes into contact with water, its molecular structure changes and becomes NH4+: ammonium.
Ammonium is the ionized form of ammonia and is a polyatomic cation, which means that it is a positively charged ion. It can be used to create derivatives such as ammonium salts like ammonium nitrate (NH4NO3) or ammonium chloride (NH4Cl).
Quels sont ses risques
The risks related to ammonia and ammonium are numerous since they can be inhaled, ingested or in contact with the skin. In the case of contact with the skin, significant irritation can be felt.
When it comes to inhalation or ingestion, depending on the concentration and time in contact, the risks to human health can be temporary lung problems, burns, unusual bleeding and in extreme cases death from pulmonary oedema.
How ammonia can be removed from water
To remove these contaminants from water, physical-chemical or biological processes can be used. These include chlorination, ion exchange and nitrification.
Chlorination can work if the amount of chlorine used is above the critical point. Although ammonium is removed from the water, chlorine compounds can take its place, such as trihalomethanes (THMs).
Ion exchange can be an interesting option since ammonium cations can be exchanged for zeolite anions. However, this technique is very expensive.
Enfin, les techniques de nitrification sont relativement complexes et variées et mérite un article a eux-mêmes, alors nous ne les aborderons pas ici.