In aeration/degasification, substances dissolved in water are brought into contact with the gas phase (air). As a result of concentration differences, substances pass into the water phase (e.g. the addition of oxygen) or out of the water phase into the gas phase (e.g. carbon dioxide removal). The speed of the transfer is determined by the difference in concentration between the gas and water phases and by the properties of the substance in question, such as its solubility in water.
Systems such as cascade aerators, strippers (stripping towers with packing material, plate aerators) and vacuum installations (vacuum degassers which create a vacuum and reduce the solubility of the product in the water phase), can be used for aeration and degasification.
Logisticon has built up a lot of experience in the use of stripping towers and multiple plate aerators for both the removal of easily-strippable substances (volatile organic hydrocarbons) and the more difficult substances (ammonium/ammonia removal at a low pH).
In addition to the usual methods such as stripping and vacuum degasification, Logisticon also uses a technology based on membranes.
It is possible to remove gas from a water phase using Liqui-cel® membrane. Liqui-cel® membrane consists of thousands of Celgard® hollow fibre membranes (similar to tiny straws), made of microporous polypropylene, which are wound around a distribution pipe. Because the hollow fibre membranes are hydrophobic, the watery flow cannot penetrate the pores, but the gas can.
If very low dissolved gas contents are the objective, it is possible to apply a vacuum to the suction side, possibly in combination with a stripping gas (often nitrogen). Oxygen levels < 20 ppb can be achieved in this way. Industrial quality nitrogen is used for this purpose rather than technically-pure nitrogen and this yields considerable savings in the operational costs. For more information : www.liqui-cel.com