Good modelling practice in applying computational fluid dynamics for WWTP modelling

Abstract

Computational fluid dynamics (CFD) modelling in the wastewater treatment (WWT) field is continuing to grow and be used to solve increasingly complex problems. However, the future of CFD models and their value to the wastewater field are a function of their proper application and knowledge of their limits. As has been established for other types of wastewater modelling (i.e. biokinetic models), it is timely to define a good modelling practice (GMP) for wastewater CFD applications. An International Water Association (IWA) working group has been formed to investigate a variety of issues and challenges related to CFD modelling in water and WWT. This paper summarizes the recommendations for GMP of the IWA working group on CFD. The paper provides an overview of GMP and, though it is written for the wastewater application, is based on general CFD procedures. A forthcoming companion paper to provide specific details on modelling of individual wastewater components forms the next step of the working group.

Towards a robust CFD model for aeration tanks for sewage treatment – a lab-scale study

“…However, oversimplification of the CFD model and a lack of calibration will lead to errors in the simulation results and validation data. Moreover, despite the vast opportunities for the use of CFD modeling in wastewater engineering, a lack of educational support, training and targeted guidelines has been recognized as a core reason for frequent software misuse by inexperienced users (Wicklein et al, 2016), usually originating from incorrect problem statement, poor model choice, incorrect setup assumptions or misinterpretation of the results (Nopens et al, 2012).…”

Hydrodynamic analysis of an axial impeller in a non‐Newtonian fluid through particle image velocimetry

“…It is recognized as one of the WWTP processes that would most benefit from a deeper understanding of its mixing process at large volumes . The lack of hydrodynamic experiments combined with little validation studies using CFD models for AD mechanical mixers might explain the large uncertainties associated with these models . As for anaerobic digestion, even fewer work has been made to obtain local hydrodynamic data for mechanical mixers.…”

Assessing flow segregation and mixing by modeling residual disinfectant conversion

“…Specifically, CFD models have been used to provide spatially resolved predictions of pathogen inactivation, disinfectant residual, and DBP formation (Angeloudis, Stoesser, & Falconer, ; Greene, Farouk, & Haas, ; Greene, Haas, & Farouk, ); three‐dimensional (3D) laser‐induced fluorescence was used to directly observe mixing in bench‐scale ozone contactors (Kim, Elovitz, Roberts, & Kim, ; Kim, Nemlioglu, Roberts, & Kim, ) and ultraviolet reactors (Gandhi, Roberts, & Kim, ; Gandhi, Roberts, Stoesser, Wright, & Kim, ); and a reactive tracer (i.e., ammonia) was used to observe mixing in a wastewater nitrification reactor equipped with axial mixers (Gresch, Braun, & Gujer, ). However, CFD modeling remains too computationally intensive for everyday reactor design and operation (Laurent et al, ), particularly for unsteady flows (Wicklein et al, ); 3D laser‐induced fluorescence is not applicable to full‐scale reactors (Kim, Nemlioglu, et al, ); and most drinking water treatment reactors (e.g., ozone contactors, clearwells) are unlike the nitrification reactor studied in some important ways (e.g., reactors are often baffled to encourage plug flow rather than actively mixed, and target contaminants do not lend themselves to real‐time measurement).…”