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Updated: Dec 23, 2025

Determination of the Settling Rate of Clay/Cyanobacterial Floccules
Published on: June 11, 2018
Quantifying the sources of uncertainty when calculating the limiting flux in secondary settling tanks using iCFD
Estelle Guyonvarch1, Elham Ramin1, Murat Kulahci2
1Department of Environmental Engineering, Technical University of Denmark (DTU), Miljøvej 113, 2800 Kgs. Lyngby, Denmark
Abstract:
Solids-flux theory (SFT) and state-point analysis (SPA) are used for the design, operation and control of secondary settling tanks (SSTs). The objectives of this study were to assess uncertainties, propagating from flow and solids loading boundary conditions as well as compression settling behaviour to the calculation of the limiting flux (JL) and the limiting solids concentration (XL). The interpreted computational fluid dynamics (iCFD) simulation model was used to predict one-dimensional local concentrations and limiting solids fluxes as a function of loading and design boundary conditions. A two-level fractional factorial design of experiments was used to infer the relative significance of factors unaccounted for in conventional SPA. To move away from using semi-arbitrary safety factors, a systematic approach was proposed to calculate the maximum SST capacity by employing a factor of 23% and a regression meta-model to correct values of JL and XL, respectively - critical for abating hydraulic effects under wet-weather flow conditions.
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