Mass transfer and reaction in a biofilm airlift suspension reactor

Abstract

Mass transfer and reaction were studied in a lab-scale biofilm airlift suspension reactor. A new approach for the determination of liquid–solid mass transfer coefficients in biofilm systems under reacting conditions is presented. The method is based on the analysis of oxygen consumption in a biofilm airlift suspension reactor and a biological oxygen–monitoring system and allows the independent estimation of gas–liquid and liquid–solid mass transfer coefficient and biofilm reaction rate. The influence of some operating conditions (solid loading, particle size and gas flow rate) on the liquid–solid mass transfer coefficient in biofilm airlift suspension reactors was investigated and a correlation for the mass transfer to biofilm-coated particles is proposed. Liquid–solid mass transfer to biofilm particles was proven to be mainly influenced by gas velocity, whilst particle size and solid loading had minor effect. The liquid–solid mass transfer coefficient measured for biofilm-coated particles was found to be smaller (by a factor varying from 5 to 25%) than the values reported for rigid particles.