Application of Computational Fluid Dynamics in Sedimentation Tank Design and Its Recent Developments: a Review

Sedimentation tanks are the workhorses of both water treatment plants (WTPs) and waste water treatment plants (WWTPs) and are crucial cogs in their respective treatment machinery. Therefore, it is desirable to operate them at maximum efficiency. But sedimentation tanks are usually overdesigned with a large safety factor to make up for the lack of knowledge and be safe from failures that may be of biological, physicochemical, or hydraulic origin. A new era of settling tank design began after the advent of computational fluid dynamics (CFD). Rapid development in the design and optimisation of sedimentation tanks had taken place since then. This paper aims to provide a review of the state-of-the-art in applying CFD in sedimentation tank design and analysis, focussing on the main factors that affect its hydrodynamics - density current, inlet and outlet configuration, baffle structures, wind, and a special type of settling tank called lamella settler or inclined plate settler (IPS), whose design may be the saviour for the numerous ageing settling tanks currently in existence. Although improvement in settling tank design went up by leaps and bounds in recent years with the help of CFD, researchers still have to compromise on many vital areas due to lack of computational power. However, with exciting revolutionary developments in computational technology like quantum computing that promises a monumental leap in computational power, a full-scale realistic transient simulation of settling tank incorporating sub-models for flocculation, sludge rheology, thermal, and wind all at once is hopeful in the near future.