DESIGN AND VERIFICATION OF A MODEL SECONDARY CLARIFIER FOR ACTIVATED-SLUDGE

A model clarifier was designed using conventional methods for the surf ace calculation and an alternative pathway for the determination of th e height and constructed accordingly. In addition, a new approach was used to evaluate the necessary scraper speed in comparison to full-sca le clarifiers. Scaling effects were taken into account. The model clar ifier was first tested by tracer experiments. Conductivity measurement s were used for the clarification zone, whereas the thickening zone wa s tested using pyrene as an organic tracer compound. Finally, the beha viour of the model clarifier was compared with a full-scale settler. T he results indicated that operation of the model clarifier was represe ntative of full-scale behaviour, except for severe overloads. Hence, t he small-scale clarifier qualified as a model for small-scale studies and could be installed on large-scale plants to monitor more transpare ntly plant performance and sludge behaviour.