Computational fluid dynamics-based design of anoxic bioreactor zone in wastewater treatment plant

Hydrodynamics-based design of an anoxic bioreactor tank is one of the serious challenges in wastewater industry. Poor fluid flow may cause settlement and therefore reduce the biological performance of a bioreactor. Whilst, a successful bioreactor design can facilitate the enhancement of biological process efficiency and reduction of energy consumption so that the investment and operation cost can be kept as low as possible. In the present study, three-dimensional computational fluid dynamics models for three common full-scale bioreactor configurations were simulated using a single-phase flow model and the standard two-equation SST k–ε turbulence model. The main objective of this numerical study is to investigate the effect of bioreactor geometry on the hydrodynamics performance of the flow field. Four submerged impellers were modelled for each tank geometry and three thrust scenarios were considered in order to evaluate the effect of changing impeller thrust on the flow velocity distribution inside each tank. The results show that the orbal bioreactor geometry has better performance in driving the flow field with more uniform flow patterns than other bioreactor configurations. The minimum flow velocity required was achieved in orbal tank to maintain the micro-organism particles suspended in the wastewater media at certain mixing power.