A one-dimensional clarifier model was assessed for its capability to describe dynamic full-scale sludge concentration profiles by using the settling properties calibrated with batch settling curve data collected by a SettloMeter((R)) . These sludge concentration profiles and batch settling tests formed part of a detailed one-month measuring campaign on a full-scale wastewater treatment plant; the measurements showed a daily variation in settling properties. Using the settling properties obtained from batch settling tests and a one-dimensional model without dispersion, the dynamics of the full-scale clarifier were analysed and the need for dispersion clearly shown. The parameters of the dispersion model were estimated from the full-scale sludge concentration profiles. The settling properties of activated sludge can be automatically determined by fitting the model to the on-line batch settling curve measurements and are needed as input to the one-dimensional model. This model can therefore be used for operation and control. The dispersion model parameters have to be determined from dynamic sludge concentration profiles but are assumed to be constant for a specific clarifier. (c) 2005 Society of Chemical Industry