The present invention relates to a process for treating sludge by the combined action of electro-osmosis and pressure. This process comprises providing a cell for treating the sludge, the cell comprising at least two electrodes including at least one cathode and at least one anode. At least one of the electrodes is movable, and at least one of the electrodes is perforated so as to drain effluents. Then, the sludge is introduced into the cell between the at least two electrodes, each of the electrodes defining a surface adapted to constantly contact the sludge. Then, the sludge is submitted to an electric current by applying a voltage to the electrodes, and applying a pressure to the sludge. by means of the at least one movable electrode so as to permit a constant contact between the surfaces and the sludge. An apparatus for carrying out such a process is also disclosed.