Abstract: This device brings microorganisms into contact with liquids as required, for example, in the treatment of sewage. The device comprises a hollow main shaft into which the inner ends of coiled process elements or process tubes are inserted and fixed. Each tube is coiled in increasing diameters at right angles around the shaft. The shaft is placed in a tank partially immersing the tubes such that when the shaft rotates the open end of each tube, into which liquid enters, alternatively passes through the liquid and the surrounding atmosphere, then the liquid, and so on. Liquid picked up during previous revolutions rotates through the tubes and eventually discharges into and through the hollow main shaft to a receiving wheel. In this way, discrete volumes of liquid pass sequentially through the tubes and are brought in contact with the microorganisms on the inner surface of the tubes.