Patent ID: 8079573

Claim:
Apparatus for aerating waste water, comprising a container for waste water and a rotor which is rotatable about a substantially vertical axis, wherein the downward directed part of the rotor is configured to reach into the waste water, wherein the rotor comprises blades having surfaces which are oriented substantially radially and vertically, wherein one or more blades comprise a straight main part and a straight upper edge part, wherein the straight main part is oriented parallel to the vertically aligned rotor axis, and wherein the straight upper edge part is oriented at an angle of between 10° and 60° with respect to the straight main part; and wherein the rotor is positioned in the container such that at least a portion of the straight upper edge part of one or more blades extends above the water surface, and wherein the transition between the straight main part and the straight upper edge part is curved, and wherein the curved transition region has a radius which is at least 0.02 times the diameter of the rotor.