Alpha factor is the ratio of the oxygen transfer rate in wastewater to the oxygen transfer rate in clean water. Alpha factor is dependent on the aeration device used and also on the presence of chemicals such as surfactants in the wastewater.

Jet aerators produce a high alpha factor in pulp and paper mill wastes. The high alpha factor is due to the presence of surfactants in pulp and paper wastewater.

Oxygen transfer is enhanced due to the high shear at the gas/liquid interface. Typical alpha factors achieved with various aeration devices are shown below.

High shear aeration devices such as jet aerators yield a higher alpha factor due to surface renewal at the gas/liquid interface. Low shear aeration devices such as fine bubble diffusers (membrane or ceramic) yield a lower alpha factor because of insufficient renewal (oxygen saturation) at the gas/liquid interface.

All aeration systems are standardized for performance at standard conditions. Therefore, the process oxygen (AOR) is converted to standard oxygen (SOR) and is inversely proportional to the alpha factor. For this reason aeration systems with low alpha factors must be designed for a higher SOR.

Jet aeration systems use less energy than other diffused aeration systems. In actual wastewater treatment plants, side-by-side comparisons have shown energy reductions of up to forty percent. Figures are similar when compared with pure oxygen or mechanical aeration systems.

Jet aerators have replaced low and high speed aerators at several installations. Lower operating power and lower maintenance costs have been the reason for all replacements.