Application of Computational Fluid Dynamics in an Outer Channel of Orbal Biological System

Orbal Biological System (OBS) is one of the modified oxidation ditches claimed as the most energy efficient, safest, and has the lowest maintenance. The OBS can be modified to meet a wide assortment of influence conditions and effluent requirements. There are three channels in OBS, outer channel, middle channel, and inner channel. The outer channel of OBS has the largest volume among the three channels, which is about 50% of the system’s total volume. It is crucial to study the operating system of the outer channel of OBS as it contributes to the highest energy consumption in the system. The computational fluid dynamics (CFD) model is developed to have a better picture of the OBS. The simulation in CFD was used to study the behaviour of the influence in the outer channel of OBS and the velocity distribution for different operating conditions in the outer channel of OBS. The result of the CFD model was used to study the relationship between the velocity and the number of aeration discs being used. This study shows that the volume fraction of water is higher at the bottom of the ditch, while the volume fraction of air is higher at the top surface of the ditch. This shows that the CFD model can represent the OBS in reality. From the model created, the velocity inside the ditch decreases when the water is deeper. The research provides a better understanding of the model flow behaviour of a biological treatment system using the simulation tool and can contribute to a better design of wastewater treatment process models in future.