A mixer/aerator described herein may characterize in one aspect as includes a parallel spaced apart array of discs mounted on a drive shaft. Each disc includes flow apertures separated by spokes. Each spoke is shaped to induce a fluid flow through a corresponding flow aperture, wherein the flow aperture trails a trailing edge of the spoke relative to the rotational direction of the discs to thereby induce a columnar fluid translation of the fluid through the array of discs while simultaneously driving the fluid laterally radially outwardly relative to the discs. Upper discs urge the corresponding columnar fluid translation downwardly, and lower discs urge the corresponding columnar fluid translation upwardly. At least one annular turbulent-mixing passageway is formed between the upper discs and the lower discs wherein said upward and downward columnar fluid translations of the fluid mix while being forced radially outwardly relative to the discs.
