Process for sludge removal from sedimentation tanks and ponds

To remove sludge/water mixtures from sedimentation tanks, in the region of the point of a funnel bottom extending over the length of the tank there is arranged a take-off line (16) provided with side walls (18) parallel to the funnel which is closed at one end and is connected at the other end to a pump shaft containing a pump and between its ends contains inlet orifices (20) on the underside. The inlet orifices (20) are matched according to spacing and/or cross-section to the differential pressure produced by the pump and decreasing along the take-off line and contain valve bodies which are guided so as to be freely movable each having two sealing surfaces opposite each other which reach a first closing position under their own weight and reach a second closing position under the reduced pressure in the take-off line and during the intermediate valve stroke clear the inlet orifice (20) for a period which can be set by the differential pressure and by their own weight (Fig. 3).