Abstract: The disclosure relates to a device for the purification of waste water with the aid of active silt, comprising an open basin or the like with supply and discharge means for the water, in which basin a partition is provided in such a manner that a closed circulating channel is obtained, a rotatable aerator with a vertical axis being mounted in such manner and adapted to be driven in such a sense that on rotation thereof the water is circulated in said closed channel, characterized in that one or more aerator are mounted near an outer wall or a partition of the basin.

Abstract: A device for aerating liquid in a tank comprises a rotating body having vanes which contact the surface of the liquid. A splash guard is disposed above the body to reflect into the tank liquid droplets discharged upwardly by the body.