Kinetics of thermophilic anaerobes in fixed-bed reactors

The main objective of this study is to estimate growth kinetic constants an d the concentration of "active" attached biomass in two anaerobic thermophi lic reactors which contain different initial sizes of immobilized anaerobic mixed cultures and decompose distillery wastewater. This paper studies the substrate decomposition in two lab-scale fixed-bed reactors operating at b atch conditions with corrugated tubes as support media. It can be demonstra ted that high microorganisms-substrate ratios favor the degradation activit y of the different anaerobic cultures, allowing the stable operation withou t lag-phases and giving better quality in effluent. The kinetic parameters obtained - maximum specific growth rates (mu (max)) non-biodegradable subst rate (S-NB) and "active or viable biomass" concentrations (X-V0) - were obt ained by applying the Romero kinetic model [L.I. Romero, 1991. Desarrollo d o un modelo matematico general para los procesos fermentativos, Cinetica do la degradacion anaerobia, Ph.D. Thesis, University of Cadiz (Spain), Serv. Pub. Univ. Cadiz], with COD as substrate and methane (CH4) as the main pro duct of the anaerobic process. This method is suitable to calculate and to differentiate the main kinetic parameters of both the total anaerobic mixed culture and the methanogenic population. Comparison of experimental measur ed concentration of volatile attached solids (VSatt) in both reactors with the estimated "active" biomass concentrations obtained by applying Romero k inetic model [L.I. Romero, 1991. Desarrollo de un modelo matematico general para los procesos fermentativos, Cinetica de la degradacion anaerobia, Ph. D. Thesis, University of Cadiz (Spain), Serv. Pub. Univ. Cadiz] shows that a large amount of inert matter is present in the fixed-bed reactor. (C) 200 1 Elsevier Science Ltd. All rights reserved.