The biofilm airlift suspension extension reactor - II: Three-phase hydrodynamics

Tilt: biofilm airlift suspension extension (BASE) reactor is a three-phase reactor, developed for nitrification and denitrification. It consists of an internal-loop airlift reactor (with liquid, air bubbles and biofilm partic les) extended with an external concentric downflowing fluidised bed (with l iquid and biofilm particles, the extension). Previously a model was develop ed, which describes the hydrodynamic behaviour of the reactor. A pilot-scal e reactor was constructed (height 6 m, volume 1.7 m(3)), and for two phases (water and air) successful validation of the model was reported. In this p aper validation has been extended to three-phase systems with either polyst yrene or silver sand. The hydrodynamic trends which were observed could be predicted by the model, however the gas hold-up was overestimated at high g as velocities and solid hold-ups (more than 20%). Due to the special design of the reactor the liquid velocity in the extension can be manipulated by the overpressure in the headspace, therewith controlling the nitrogen remov al efficiency. (C) 1999 Elsevier Science Ltd. All rights reserved.