Abstract: An Aerator/Digester for treating wastewater comprises cylindrical chamber having a centrally disposed air pipe supported from the chambers closed bottom end and extending along a longitudinal axis of the cylindrical chamber and beyond the upper end. The air pipe includes at least one aperture pattern comprising plural interleaved rows of relatively small diameter holes and larger diameter holes. When air under pressure, is introduced through the air pipe, a Venturi effect is created to draw wastewater into the chamber via ports formed near the closed bottom end and out via one or more outlet ports proximate to the upper end. The apertures are drilled through the air pipe at an angle to the vertical with the small diameter apertures inclined at an upward angle and the larger diameter apertures at a downward angle which has been found to enhance the circulation of the wastewater.