Computational Fluid Dynamics Model of BioCAST Multienvironment Air-Lift Bioreactor

Abstract

A computational model was developed to study the hydrodynamic characteristics of a new multienvironment air-lift bioreactor. This model study considerably expands on the laboratory experiments by exploring the hydrodynamic characteristics of multiple combinations of geometries and operating conditions and by providing a visual illustration of the liquid-phase flow patterns. The model was first tested against preliminary laboratory results to ensure its validity. This included comparing two simplified geometries for the three-disc prototype air sparger assembly to determine which led to results closer to laboratory measurements. A torus geometry was found to better represent the prototype than a single disc. The model was modified to evaluate the hydrodynamic characteristics of alternative operating conditions and physical geometries beyond what would be possible in the laboratory. The flow pattern in the outer clarifier zone was shown to be very sensitive to the geometry of the bioreactor wall separating the clarifier from the inner microaerophilic zone. Establishing a smooth, upward flow pattern in the clarifier was shown to be possible only when the clarifier was sufficiently shielded from the circulation in the anoxic cone below. Further research is needed to quantify the effect of hydrodynamic characteristics on contaminant removal efficiency.