Activated sludge models now in use worldwide for the design and operation of treatment
systems use hypothetical concentrations of active organisms. In order to validate and
calibrate model outputs, concentrations and activities of organisms responsible for
nitrification and denitrification need to be reflected by actual measurements. This
research has been initiated by the observation of an increasing gap of suitable techniques that exist in the direct measurement and separation of active biomass components, responsible for COD removal and denitrification.
