Abstract: Pumping apparatus for collecting polluted liquids such as oil on water and including a first pumping stage comprising a rotatable annular rotor having curved blades shaped to draw liquid inwardly towards the center of rotation, and stationary blades disposed within the rotor blades to receive liquid into the spacers between them, and a further pumping stage having rotatable blades shaped to receive the liquid from the stationary blades and deliver it under pressure in an upward direction to an outlet. The pumping apparatus may be mounted on a flotation unit which is suitable for collection of oil from the surface of water.