MEASUREMENTS OF DISSOLVED OXYGEN IN ATTACHED MICROBIAL FILMS OF ROTATING BIOLOGICAL CONTACTOR BY OXYGEN MICROELECTRODE

Abstract

As for rotating biological contactors, no measurement result has been reported as yet on dissolved oxygen (DO) concentration as well as substrate concentration both inside and outside the biofilm on the disk surface. The DO profile should be known for precisely determining the rates of substrate oxidation and studying the substrate removal phenomena. The authors developed a special oxygen microelectrode to measure DO. The conclusions in this study are summarized as follows: (1) Water layers attached on the biofilms in the air phase are about 50 μm in thickness; (2) DO concentrations in the liquid layers and in the biofilms become higher depending on the retention time in the air phase; (3) The biofilms swell when submerged into the liquid phase, and DO concentrations in the biofilms suddenly become lower; (4) The DO concentration gradient exists between the bulk liquid and the biofilm surface; (5) The DO concentration profiles in the film change locally and significantly, and differ from the averaged ones in the previous models.