This work applies computational fluid dynamics (CFD) modelling to a novel 1000 L design of single-use-technology (SUT) bioreactor, with a magnetically driven floor-mounted impeller and spargers distributed across the tank floor. A two-phase Euler-Euler model using the k-epsilon turbulence model and population balance is presented alongside the use of immersed solid method for modelling the impeller motion. This work also provides the first CFD analysis of a large-scale SUT bioreactor, identifying key flow characteristics of the non-standard design at different operating conditions. Five models for the mass transfer coefficient, k(L), are compared, with k(L)a values compared to experimental measurements. The slip velocity model is found to be the best prediction of the mass transfer coefficient for this SUT system. Separating the influence of the mass transfer coefficient and specific area, a shows that the latter is the dominant driving force behind changes in k(L)a that occur at different operating conditions. Comparing the present work to previous studies for traditional stirred tanks highlights the need for understanding the hydrodynamics of non-standard reactor designs when identifying suitable mass transfer models in gas-liquid flow systems. (C) 2018 Elsevier Ltd. All rights reserved.