Collector apparatus

Pumping apparatus for collecting polluted liquids including a pumping unit comprising a stationary casing, an inlet and an outlet on said casing, a substantially vertically oriented drive shaft rotatably mounted in said casing, drive means operably connected to said drive shaft to drive said shaft about its substantially vertically oriented axis, a first pumping stage comprising a first annular rotor mounted for rotation on the lower end of said drive shaft and below said casing, forming the lower extremity of the apparatus, first blades mounted on the peripheral region of said first rotor at said inlet, shaped and operably arranged to pump liquid substantially radially inwardly with respect to the axis of rotation, stationary blades mounted on the lower extremity of said casing adjacent said inlet substantially between said first blades and said axis of rotation shaped and operably arranged to guide said liquid from said first blades substantially radially inwardly, and a further pumping stage comprising a second rotor mounted for relative rotation with respect to said casing and said drive shaft and in concentric surrounding relationship with respect to said shaft, gear means operably engaging between said drive shaft and said second rotor to drive said second rotor at higher rotational speed than said first rotor, second blades mounted on said second rotor adjacent the radially inner edges of said stationary blades shaped and arranged to pump said liquid from said stationary blades under pressure to and through said outlet.