A one-dimensional model of the process of continuous sedimentation in a clarifier–thickener unit is
presented. The governing model is expressed as a system of two nonlinear partial differential equations
for the solids volume fraction and the varying settling velocity of the solids as functions of depth and
time. This model extends the well-known model for the dynamics of a flocculated suspension in a
clarifier–thickener advanced by Bürger et al. (2005). Operating charts are calculated to be used for the
control of steady states, in particular, to keep the sediment level and the underflow volume fraction at
desired values. A numerical scheme and a simple regulator are proposed and numerical simulations
are performed.