Related Experiment Video
Updated: May 4, 2026

Mesocosm-Scale Constructed Wetland Design for Wastewater Treatment
Published on: May 2, 2025
Dynamic one-dimensional modeling of secondary settling tanks and design impacts of sizing decisions
1Civil and Environmental Engineering Department, University of California, 5732 Boelter Hall, Los Angeles 90095-1593, USA.
Abstract:
As one of the most significant components in the activated sludge process (ASP), secondary settling tanks (SSTs) can be investigated with mathematical models to optimize design and operation. This paper takes a new look at the one-dimensional (1-D) SST model by analyzing and considering the impacts of numerical problems, especially the process robustness. An improved SST model with Yee-Roe-Davis technique as the PDE solver is proposed and compared with the widely used Takács model to show its improvement in numerical solution quality. The improved and Takács models are coupled with a bioreactor model to reevaluate ASP design basis and several popular control strategies for economic plausibility, contaminant removal efficiency and system robustness. The time-to-failure due to rising sludge blanket during overloading, as a key robustness indicator, is analyzed to demonstrate the differences caused by numerical issues in SST models. The calculated results indicate that the Takács model significantly underestimates time to failure, thus leading to a conservative design.
Related Concept Videos
Design Example: Creating a Hydraulic Model of a Dam Spillway
Typical Model Studies
Modeling and Similitude
Dimensional Analysis
In fluid mechanics, dimensional...
Conservation of Mass in Moving, Nondeforming Control Volume
In the context of a detention basin, the conservation of mass states that the total mass of water entering the basin must equal the mass leaving the basin plus any accumulation of...
Design Example: Design of an Irrigation Channel

