Abstract: Apparatus for draining of muddy liquids, especially of sludges and slurries in sewage clarification plants, where first of all an ionic coagulant, eg., an anionic or cationic coagulating agent, is added to the muddy liquid in a first ionic coagulating means to obtain an aqueous sludge which is separated from the muddy liquid in a first coagulating chamber by sedimentation in a straining zone and wherein the aqueous sludge is subsequently filtered and pressed, whereafter the liquid is treated in a second coagulating or mixing chamber.The apparatus to carry out the process comprises in addition to the first coagulation chamber coagulation chamber for the muddy liquid, a revolving screening belt constituting the filtering means for the straining zone and a series connected revolving screen belt press which aids in dewatering the filtered solids.