The paper presents a simple analytical model of the hydrodynamics of a hybrid airlift apparatus with an external liquid circulation loop. The apparatus consists of two sections: a two-phase fluidization column and a barbotage section. The advantage of such a configuration is that there is no contact between the gas phase and the solid phase, which is relevant in case of processes involving a biofilm immobilization on fine carrier particles. Then, the shear stresses produced by passing bubbles do not damage the surface of a biofilm. The proposed model was derived based on the global momentum balance. It allows to determine basic hydrodynamic parameters of the apparatus including liquid and gas velocity, gas hold-up, and porosity and height of the fluidized bed. The model was verified experimentally and the hydrodynamics of the selected zones of the apparatus was simulated using Computational Fluid Dynamics (CFD). (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.