Airlift Bioreactors: Review of Recent Advances

1 The present review roughly covers the publications that have appeared since Prof. K. Schügerl delivered a keynote address at the 4th GLS International Conference in 1997 (Schügerl, 1997). It includes publications that deal with gas/liquid systems without solids, but gives an extra weight to applications of airlift bioreactors to wastewater treatment and to algal growth. Three extensive reviews have been published lately (Chisti, 1988; Merchuk and Gluz, 1999; Petersen and Margaritis, 2001). Most of the publications selected for this review are not considered. The material is presented under several subtitles ‘fluid dynamic characterization’ briefly describes some of the reported data on gas holdup, liquid velocity and mass transfer in airlift reactors. A section on ‘models’ follows. This is a field in which several very relevant papers have been published. These papers are critically reviewed, trying to enlighten common characteristics and differences among the approaches adopted. ‘Wastewater treatment’ is discussed next, because of the relevance of the subject and of the close relationship to the modeling section, since some of the most interesting mathematical models were developed in relation to wastewater. A short review of some of the design modifications proposed is then presented, followed by a review of some of the bioprocesses that have been developed choosing airlift reactors. Among these, algal growth has been given special consideration.