Degasification

Dissolved gases are present in all naturally occurring waters: Oxygen and nitrogen are picked up from the atmosphere; Hydrogen sulfide is absorbed from underground organic deposits; Carbon dioxide is picked up from the atmosphere, from decaying organic material and from minerals in the earth. Hydrogen sulfide and carbon dioxide can be removed or reduced by aeration of the water. Forced draft decarbonation is a common method of doing this. A forced draft decarbonator is a relatively simple water treatment device. Incoming water is sprayed into a tower filled with packing material.

The drops of water that flow down through the tower strike the packing material and form a thin film on the packing material surface, encouraging the release of excess carbon dioxide. A centrifugal fan creates an updraft of air through the tower (thus the name 'forced draft') to carry away the released carbon dioxide gas. The carbon dioxide gas exits through a vent at the top of the unit. Many factors influence the creation of carbon dioxide and its removal from the service water: The amount of carbon dioxide in the surrounding atmosphere; the local pressure; the pH of the water; and the presence of bicarbonate ions.