An operational dynamic model of the final clarifier

Abstract

The theory behind the dynamics of the final clarifier of the sludge plant is reviewed and the corresponding distributed parameter model is discussed. Since this full model is too complicated for on-line use, a simplified, lumped-parameter model is derived, which has the following three state variables : sludge blanket height and mean sludge concentrations above and below the sludge blanket height. It has been calibrated and validated with routine measurements from a real clarifier. The conclusion is drawn that the simplified model describes well the dynamics of the clarifier and, therefore, may be used for various real-time control purposes. For example, when combined with an adaptive parameter estimation algorithm, the model can be used to monitor the settling characteristics of the sludge without measuring sludge volume index.