Submersible propeller pump for pumping and circulating activated sludge in wastewater treatment plants, especially for the denitrification/nitrification process. It is intended for large flow and low heads between 0.1 and 1.8 m (4 - 71 in). In contrast to conventional axial flow pumps, recirculation pumps do not require expensive structures in the tank. The unit is lowered along a guide tube and connected by an automatic coupling system to the pipeline.
