Anaerobic digestion of molasses by means of a vibrating and non-vibrating submerged anaerobic membrane bioreactor
De Vrieze, Jo × Hennebel, Tom Van den Brande, Jens Bilad, Ro'il M Bruton, Thomas A Vankelecom, Ivo Verstraete, Willy Boon, Nico #
Biomass & Bioenergy vol:68 pages:95-105
Bio-refineries produce large volumes of waste streams with high organic content, which are potentially interesting for further processing. Anaerobic digestion (AD) can be a key technology for treatment of these sidestreams, such as molasses. However, the high concentration of salts in molasses can cause inhibition of methanogenesis. In this research, concentrated and diluted molasses were subjected to biomethanation in two types of submerged anaerobic membrane bioreactors (AnMBRs): one with biogas recirculation and one with a vibrating membrane. Both reactors were compared in terms of methane production and membrane fouling. Biogas recirculation seemed to be a good way to avoid membrane fouling, while the transmembrane pressures in the vibratingMBR increased over time, due to cake layer formation and the absence of a mixing system. Stable methane production, up to 2.05 L L_1 d_1 and a concomitant COD removal of 94.4%, was obtained only when diluted molasses were used, since concentrated molasses caused a decrease in methane production and an increase in volatile fatty acids (VFA), indicating an inhibiting effect of concentrated molasses on AD. Real-time PCR results revealed a clear dominance of Methanosaetaceae over Methanosarcinaceae as the main acetoclastic methanogens in both AnMBRs.