The inverse turbulent bed:: A novel bioreactor for anaerobic treatment

An inverse turbulent bed was investigated for anaerobic digestion. In this reactor, a granular floating solid is expanded by an up-flow current of gas. The carrier particles (Extendospheres(R)) were chosen for their large specific surface area (20000 m(2) m(-3)) and their low energy requirements for fluidization (gas velocity of 1.5 mm s(-1), 5.4 m h(-1)). It was tested with wine distillery wastewater and presented promising performances after 90 days of operation: 75-85% carbon removal with an organic loading rate of 15 kg(COD) m(-3) day(-1). The amount of biomass (in terms of attached volatile solids) was close to 0.2 g g(-1) of solid at the end of the tests. Most particles were covered with a thin biofilm of uniform thickness, which was attributed to the friction effects due to turbulence. The performance observed during the start-up was similar or even higher than that of other previously tested fluidized bed technologies treating the same wastewater. (C) 1999 Elsevier Science Ltd. All rights reserved.