In this study, the effects of liquid phase rheology on the hydrodynamics of a pilot scale bubble column reactor is extensively investigated by applying various types of test liquids with different rheological characteristics as the operating fluids. Two fiber optic probes and several pressure transducers are used and different time domain and frequency domain analyses are applied to perform a comprehensive interpretation of the pressure signals and measure the hydrodynamic parameters of the gas phase. A new approach is proposed based on the dynamic moduli of viscoelastic solutions to better understand the simultaneous viscous and elastic effects It was observed that the elasticity of the operating liquid reduced the average bubble chord length and increased the total gas holdup. The obtained results reveal that although the viscosity is more favorable for coalescence, the elasticity of the operating liquid can prevent bubble coalescence by showing a solid like behavior at the interface of two bubbles. (C) 2015 Elsevier Ltd. All rights reserved.