Abstract: A diffuser for the treatment of waste sludge utilizes low pressure air injected from below to produce a bed capable of being handled as a fluid such as to permit pumping from a sedimentation basin to a tank truck for transport to a point of use or disposal. A system of air discharge pipes strategically located in the basin below the sludge connects with common air receiving manifold at the periphery of the basin, and a complete valve arrangement permits control of the air discharge to accommodate for all types of sludge under various conditions as required prior to and during emptying of the contents of the basin.