Rotating disk contactors - high efficiency bioreactors Part I - Oxygen Mass transfer within the liquid film

摘要

The RBC process is a fixed film either aerobic or anaerobic biological treatment process for removal of carbonaceous and nitrogenous materials from domestic and industrial wastewater. It can be used to upgrade the secondary or tertiary wastewater treatment systems. The basic elements of an RBC system are media, shaft, bearings, drive and cover. The rotating media arc used for supporting growth of microorganisms and for providing contact between the biofilm. the organic substrate, and DO. The organic substrate removal in an RBC system is dominated by mass transfer/diffusion of substrate and DO within the wastewater film and the biofilm. In heavily loaded systems, oxygen transfer controls the overall reaction rate. Understanding and prediction of kinetics of film mass transfer phenomenon is important to good engineering design and environmental solution making. Biological removals are almost always redox processes, which require two substrates, an oxidaat (oxygen) and a reductant (organic matter). The study of biofilm kinetics and of substrates mass transfer within the wastewater film and the biofilm has to establish which substrate is limiting for the removal. The substrate that is limiting for the removal is determined by the substrate that penetrates the shortest distance into the biofilm. A mathematical model based on the differential momentum and mass balance equations written for oxygen, considering a parabolic profile for wastewater film velocity in laminar wastewater film in RBC was developed.