Abstract: An apparatus for the separation of oil and other substances from a liquid such as water consisting of a first, vertical and mainly cylindrical reservoir in which separation takes place by means of gravity, a second reservoir for additional separation, and a third reservoir in which separation takes place by means of flotation such as inducing gas. The second reservoir is coated round the first reservoir over a part of the cylinder, with the third reservoir above the second reservoir and also around the first reservoir. In the wall between the first and the second reservoir, interconnecting tubes are located. The second and the third reservoir are connected with each other via an opening in a ceiling plate.