device such as a combined aeration washing and drying device fig2 illustrates an example of an inventive process and also shows the proportions in which the various waste constituents are obtained when processing average domestic waste the figure also illustrates three different alternatives for final treatment of the waste pulp produced namely fermentation as illustrated in fig1 combustion incineration or dumping the fig3 illustration includes a separator which forms part of the plant illustrated in fig1 and which includes a pulp inlet 46 to which there is connected an air inlet 48 said air inlet being connected to the pulp inlet 46 in a manner which will enable pressurized air from a fan 50 to be mixed with the pulp this admixture of air with the pulp results in the separation of light fractions such as pieces of cellulose plastic fibre foam etc which is removed with the aid of a screening drum 54 mounted on the upper part of the vessel or tank 52 centrally opposite the inlet 46 the drum 54 functions to capture the light reject and deliver said reject to an outlet 56 the vessel 52 is kept filled with pulp so as to form an upper surface which is level with the inlet 46 and the lower part of the screening drum 54 arranged down stream of the inlet 46 is a scrap trap 58 into which heavy constituents such as metal batteries etc which have not earlier been separated from the pulp are sorted out connected to the inner end of the inlet 46 adjacent the scrap trap 58 is a.