Abstract: An arrangement and method for mechanical cleaning of an active surface (4,17-20) of an instrument (5) in touch with liquid. The active surface of the instrument is exposed to cleaning media (11), which consists of separate, moving particles, enclosed into an instrument container. The motion of the cleaning media is rotational and achieved and maintained by directing an influx (9) parallel to the direction of motion (8) of the cleaning media. The influx may contain gas, liquid or mixture of gas and liquid. The cleaning media wipes clean the at least one active instrument surface.

Abstract: The invention relates to a bioreactor (1) for the purification of waters, said reactor comprising a cross-sectionally essentially circular or elliptical tank section (2) provided with inlet means (5) for water to be purified and outlet means (6) for purified water. The tank holds thereinside carrier material (3) on which a biofilm may develop. The tank is further provided with means (4) for supplying a fluid which contains a reaction gas required by the purification process, such that the water to be purified develops gas bubbles containing a reaction gas. The tank section is adapted to be essentially full of water during the purification process. The fluid supply means (4) are disposed on the tank wall and the reactor comprises control means for operating the fluid supply means in such a way that a spinning motion of the carrier, the water, and at least some of said reaction-gas bearing bubbles is effected thereby around a rotation centerline passing essentially through the tank's cross-sectional center.