To mix, or not to mix, that is the question

Abstract

The use of Computational Fluid Dynamics (CFD) in the wastewater field has long been limited to troubleshooting of design flaws. Research-wise, this has recently opened up to the potential usage of CFD in the reactor design phase. Another noticeable shift is the one from only considering plain hydrodynamics to the coupling to kinetic models and population balance models (PBM). This vastly assists in design optimisation problems that are either driven by kinetics or physical processes such as flocculation or crystallisation which lead to different optimal solutions as the goal is quite different. This contribution provides some examples of the above and discusses how the know-how should be used to develop new design methods, hereby questioning how ideal mixing should be defined.