air oxidation

These techniques use oxygen taken from unheated air at near atmospheric pressure and apply the gas-liquid exchange laws (see gas-liquid exchange and air or gas strippers, removing CO2). As a reminder:

• molecular oxygen is not a strong oxidant (see oxidation and reduction) Therefore, oxygen can only be used to oxygenate compounds that are easily oxidised such as: Fe²⁺, Mn²⁺, S^2–… ;
• oxygenating water by aeration can cause its calcium carbonate equilibrium to undergo a major and undesirable change; stripping CO₂ for instance tends to produce a scaling water with possible precipitation of calcium carbonate;
• bringing water and air in contact can be regarded as an air "wash". Consequently, the air needs to be of proper quality and, if necessary, it must be filtered (dust, sand winds, oil droplets …).

Oxidation processes can be classified according to the methods used to bring liquid and gas phases into contact :

• trickling;
• air spraying;
• air injecting into a liquid.

The transfer of oxygen into the liquid phase (required prior to any oxidation process) as the head loss generated by the aeration system, vary significantly depending on the technique applied. For instance, head loss will fluctuate from a few centimetres of water column with processes that use bubbling up to a bar with air spraying processes.