Operating charts for continuous sedimentation III: control of step inputs

Abstract. The main purposes of a clarifier-thickener unit is that it should produce a high underflow concentration and a zero effluent concentration. The main difficulty in the control of the clarification-thickening process (by adjusting a volume flow) is that it is non-linear with complex relations between concentrations and volume flows via the solution of a PDE – a conservation law with a source term and a space-discontinuous flux function. In order to approach this problem, control objectives for dynamic operation and strategies on how to meet these objectives are presented in the case when the clarifier-thickener unit initially is in steady state in optimal operation and is subjected to step input data. A complete classification of such solutions is given by means of an operating chart (concentration-flux diagram).