## Preprint 2016-05

## Sophie Balemans, Raimund Bürger, Stefan Diehl, Pierre Francois, Julien Laurent, Florent Locatelli, Ingmar Nopens, Elena Torfs:

### On constitutive functions for hindered settling velocity in 1-D settler models: selection of appropriate model structure

### Abstract:

Advanced 1-D models for Secondary Settling Tanks (SSTs) aim to explicitly account for several phenomena that inuence the settling process (such as hindered settling and compression settling). For each of these phenomena a valid mathematical expression needs to be selected and its parameters calibrated to obtain a model that can be used for operation and control. The presented work evaluates several available expressions for hindered settling based on long-term batch settling data. The analysis shows that the exponential forms which are most commonly used in traditional SST models not only account for hindered settling but partly lump other phenomena (compression) as well. This makes them unsuitable for advanced 1-D models that explicitly include each phenomenon in a modular way. A power-law function is shown to be more appropriate to describe the hindered settling velocity in advanced 1-D SST models.

This preprint gave rise to the following definitive publication(s):

**Sophie BALEMANS, Raimund BüRGER, Stefan DIEHL, Pierre FRANCOIS, Julien LAURENT, Florent LOCATELLI, Ingmar NOPENS, Elena TORFS: ***On constitutive functions for hindered settling velocity in 1-D settler models: selection of appropriate model structure*. Water Research, vol. 110, 1, pp. 38-47, (2017).