Characterization of Mixing in Aerated Lagoons

The macromixing characteristics of three mechanically aerated lagoons have been investigated using the residence time distribution approach. Four mathematical models capable of describing partially mixed behavior are fitted to the data. It is concluded that the macromixing regime is more dependent upon the lagoon geometrical parameters than upon operating parameters such as horsepower input. The pertinent correlation involved is D/(uL) = 3.10 × 10⁴ τ/L². in which τ is expressed in hours and L in feet. Based on this correlation, a suggested design procedure employing the axial dispersion model to account for partial mixing in an aerated lagoon is outlined. The unequally-sized completely mixed tanks-in-series model is particularly useful for making rapid hand calculations to analyze aerated lagoon performance.