An aerator assembly for use in the aeration vessel of a wastewater treatment system comprising a rigid tubular member having an upper end and a lower end, and a diffuser assembly, the diffuser assembly comprising a flexible connector and a diffuser head, the flexible connector connecting the diffuser head to the lower end of the rigid tubular member and providing a fluid flow path between the tubular member and the diffuser head, the upper end of the rigid tubular member being adapted to be connected to a source of an oxygen-containing gas such as air.