Degassing / Gas exchange

Gas exchange involves the removal of unwanted gases from the water or the introduction of gases such as oxygen for oxidation processes.
Both the degassing and the gas introduction / gassing are mass transport processes which take place in liquid – gaseous form through the phase interface, i.e. in which molecules of the substance to be exchanged pass from one phase to the other. The gas exchange takes place until an equilibrium (corresponding to the saturation concentrations of the respective phases) is reached.

An essential role for an intensive mass transfer is played by the turbulence of the flows and a large phase interface, which can be influenced by a corresponding energy input in each case. In practice, different designs and modes of operation of gas exchange apparatuses result, which differ in particular in the formation of the phase interface:
  • Production of a liquid film with a large surface area (e.g. in a corrugated web column)
  • Generation of gas bubbles with a large specific surface area and uniform distribution of the gas bubbles in the liquid volume (e.g. flatbed aerator)
  • Generation of liquid droplets with a large specific surface area and uniform spraying or trickling of the droplets in a gas space (atomization, Riesler)
The discharge of hydrogen sulfide and other volatile odor- and taste-forming
Substances can also be targets. In recent times, the aeration process is also used for
Removal of volatile organic halogens (CHCs), the application for reducing the concentration of the noble gas radon is foreseeable for special cases.
  • Input of oxygen (for oxidation processes)
  • Discharge of interfering gases (carbon dioxide, hydrogen sulfide, methane, etc.)
  • Physical deacidification
  • Introduction of oxygen for aerobic biological processes
  • Thermal degassing of boiler feed water
  • Membrane degassing of ultrapure water