Aeration is used in water treatment as a pretreatment in the process of removing iron and hydrogen sulfide (rotten egg smell) from water. Air is a powerful oxidizer of both iron and hydrogen sulfide. It quickly converts unfilterable ferrous iron to filterable ferric iron, and it reduces hydrogen sulfide to elemental sulfur, which is easily removed from water by a filter. Aeration removes odour and tastes due to volatile gases like hydrogen sulphide and due to algae and related organisms. Aeration also oxidize iron and manganese, increases dissolved oxygen content in water, removes CO and reduces corrosion and removes methane and other flammable gases.