Abstract
Aeration is a key and the most energy-intensive process in biological wastewater treatment using
activated sludge systems in aeration tanks, accounting for up to 50-90% of the total energy consumption
of wastewater treatment plants. The efficiency of biological treatment largely depends on providing
activated sludge microorganisms with a sufficient concentration of dissolved oxygen as well as ensuring
proper mixing of the sludge mixture within the reactor. Therefore, improving the efficiency of aeration
systems is an important task for reducing operational costs and increasing the overall sustainability of
wastewater treatment facilities.
This paper examines the theoretical foundations of the aeration process in biological wastewater
treatment systems. Particular attention is given to the mechanisms of oxygen mass transfer from the gas
phase into the liquid phase and the factors influencing this process. The key parameters characterizing
oxygen transfer efficiency are analyzed, including the volumetric oxygen mass transfer coefficient (KLa)
and the α-factor, which reflects the influence of wastewater properties on oxygen transfer. Understanding
these parameters is essential for the correct design, optimization, and operation of aeration systems
in activated sludge reactors. The presented theoretical analysis contributes to improving the energy
efficiency and operational performance of modern wastewater treatment plants.