The invention relates to a pump for pumping contaminated liquid including solid matter, comprising a pump housing provided with a rotatable impeller (3) having at least one vane (9) and an impeller seat (4), the impeller seat (4) presenting at least one recess (13) in the top surface (11) thereof, a sheering/cutting action arising between an cutting edge (15) of said recess (13) and a lower edge (14) of the vane (9) as the impeller (3) rotates relative to the impeller seat (4). Furthermore, the pump also comprises means for guiding the solid matter towards said recess (13), the guiding means comprising at least one guide in and at least one projection (20), an upper surface (19) of the guide pin extending from a position contiguous to the most inner part of the vane (9) of the impeller (3) towards the impeller seat (4), and the projection (20) protruding from the impeller seat (4).