title: 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) explicitly account for several phenomena that influence 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. This is, however, a challenging task as these phenomena may occur simultaneously. Therefore, the presented work evaluates several available expressions for hindered settling based on long-term batch settling data. Specific attention is paid to the behaviour of these hindered settling functions in the compression region in order to evaluate how the modelling of sludge compression is influenced by the choice of a certain hindered settling function. The analysis shows that the exponential hindered settling 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.
authors.affiliation: BIOMATH, Department of Mathematical Modelling, Statistics and Bioinformatics, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Ghent, Belgium. Electronic address: elena.torfs@ugent.be.
authors.forename: Elena
authors.initials: E
authors.lastname: Torfs
authors.affiliation: BIOMATH, Department of Mathematical Modelling, Statistics and Bioinformatics, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Ghent, Belgium.
authors.forename: Sophie
authors.initials: S
authors.lastname: Balemans
authors.affiliation: ICube, Département de Mécanique, Université de Strasbourg, 67000, Strasbourg, France.
authors.forename: Florent
authors.initials: F
authors.lastname: Locatelli
authors.affiliation: Centre for Mathematical Sciences, Lund University, P.O. Box 118, S-221 00, Lund, Sweden.
authors.forename: Stefan
authors.initials: S
authors.lastname: Diehl
authors.affiliation: CI(2)MA and Departamento de Ingeniería Matemática, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Casilla 160-C, Concepción, Chile.
authors.forename: Raimund
authors.initials: R
authors.lastname: Bürger
authors.affiliation: ICube, Département de Mécanique, Université de Strasbourg, 67000, Strasbourg, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Laurent
authors.affiliation: ICube, Département de Mécanique, Université de Strasbourg, 67000, Strasbourg, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: François
authors.affiliation: BIOMATH, Department of Mathematical Modelling, Statistics and Bioinformatics, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Ghent, Belgium. Electronic address: ingmar.nopens@ugent.be.
authors.forename: Ingmar
authors.initials: I
authors.lastname: Nopens
mesh_terms: D002138:Calibration; D008962:Models, Theoretical; D011312:Pressure; D012722:Sewage / Q000737:chemistry; D014865:Waste Disposal, Fluid
chemical_list: D012722:Sewage
keywords: 1-D modelling; Batch settling test; Calibration; Compression settling; Secondary clarifier