Author(s): Noor Aida Saad, Hamidi Abdul Aziz, Mohd Zulkifly Abdullah, Mohamed Zubair
Linked Author(s): Noor Aida Saad
Keywords: Orbal Biological System (OBS), Computational Fluid Dynamics (CFD), oxidation ditch, aeration devices, biological treatment.
Abstract: Orbal Biological System (OBS) has been designed to provide an optimized approach of the biological treatment process. The unique OBS aeration discs are claimed to provide high oxygen transfer and mixing efficiency. High power usage by aerators has commonly been a major issue for Extended Aeration (EA) biological system. In order to provide a better understanding of the OBS, as one type of a modified oxidation ditch, the research aims to develop a Computational Fluid Dynamics (CFD) model to visualize the water and air distribution throughout the oxidation ditch. The research aims to develop a model that can represent a full-scale OBS that may contribute to a better understanding of the unit process by assessing the current operational performance which is related to aeration shafts of the OBS. A 3D multiphase and an open channel CFD-based model have been developed to simulate the hydrodynamics in an OBS. Open channel flow modelling which takes into consideration the influence of atmospheric air provides the data of the volume fractions of water and air. The developed 3D two phases CFD model has shown a good representation of the real OBS. Variations of volume fractions are supporting the reality of the occurrence of anoxic and aerobic conditions throughout the OBS. It can also be observed that due to the mixers, the air composition is extended to at least half (50%) of the tank's depth. The volume fractions of the air are higher at the surface level compared to the bottom of OBS. This also demonstrates that the oxygen due to the mixing is facilitated by the mixers and they are effective in increasing the composition or volume fraction of oxygen throughout the ditch. These important findings are made possible due to the developed advanced CFD model which incorporating the open channel flow system
Year: 2017