Wastewater treatment with particulate biofilm reactors RID B-2738-2009

The review presented in this paper focuses on applications of particulate biofilm reactors (e.g. Upflow Sludge Blanket, Biofilm Fluidized Bed, Expanded Granular Sludge Blanket, Biofilm Airlift Suspension, Internal Circulation reactors). Several full-scale applications for municipal and industrial wastewater treatment are presented and illustrated, and their most important design and operation aspects (e.g. biofilm formation, hydrodynamics, mass transfer, mixing) are analysed and discussed. It is clear from the review that this technology can be considered a grown up technology for which good design and scale-up guidelines are available. (C) 2000 Elsevier Science B.V. All rights reserved

Identification of mass transfer parameters in three-phase biofilm reactors RID B-2738-2009

This work presents the analysis of dynamic models describing oxygen transfer and reaction in three-phase biofilm reactors. The modelling is mainly aimed at designing experiments for the estimation of mass transfer parameters in these systems. Systems with and without reaction are investigated separately and distinct approaches are used to simplify the model equations in the two cases. In order to show their limitations, simplified models are compared to a mechanistic model describing oxygen gas-liquid transfer, liquid-solid transfer, and diffusion and reaction within the biofilm. Model reliability in the estimation of the parameters is established through a sensitivity analysis. In the case of plain oxygen absorption in the liquid phase and adsorption without reaction in the biofilm layer two limiting cases are considered for slow and fast diffusion within the biofilm. When assuming fast diffusion, the simplified model has an error of less than 4% (relative to the mechanistic model) in the estimation of Volumetric gas-liquid mass transfer coefficient (k(L)a) in the case of low solid hold-up or low value of k(L)a. In the case of a reacting system, half-order and zero-order expressions for the biochemical reaction are used to calculate explicitly the oxygen flux at the biofilm surface without remarkable deviation from the values calculated through the mechanistic model. On the basis of this analysis. criteria are given to design experiments for the estimation of mass transfer parameters in three-phase biofilm reactors. (C) 1999 Elsevier Science Ltd. All rights reserved

Mass transfer and reaction in a biofilm airlift suspension reactor RID B-2738-2009

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. (C) 1998 Elsevier Science Ltd. All rights reserved