Abstract: Waste water and sludge is supplied through an inlet 12 to a flotation basin 10 where a skimmer 14 collects floating solids and sweeps sunken solids into a bottom discharge trough. Water from the basin is drawn off through a line 16 and fed by pumps 18, 20 into an air pressurized container 26 through an ejector 24 which draws in and dissolves the compressed air in the water by aspiration or eduction. The air saturated water is then fed back into the basin through valves 42, 44 where the reduced pressure releases the air in the form of micro-bubbles, which reduce the surface tension of the waste water to release sludge particles and float them to the surface for skimming off.

Abstract: An inexpensive method for drying and sterilizing sewage sludge that has previously gone through a preliminary drying process and has, on the average, a solid matter content ranging between 15 and 35% and a maximum content of 40%. The sewage sludge is dried and sterilized by breaking it into ball-like particles having diameters ranging from 1 to 10 mm and coating these particles with quicklime. The entire process can be performed using a paddle mixture. The quicklime not only reacts with the surfaces of the particles so coated but also penetrates into their interiors. The resulting chemical reaction (H.sub.2 O+CaO T Ca(OH).sub.2) dries and sterilizes the sludge, without the necessity of applying heat from an external source, directly to produce a granular product which, for example, can be used as an agricultural fertilizer which can be scattered by a conventional fertilizer spreader.