A multiscale approach for studying an anaerobic multiphase bioreactor

This work aims at developing an original micro- to mesoscale approach to investigate various phenomena at different scales within a multiphase bioreactor and then to intensify its performance. The interactions between granular sludge particles as well as the biogas production efficiency in a 2D pilot at mesoscale were studied under various hydrodynamic conditions. A particle image velocimetry (PIV) system and a high-speed camera were employed to quantify the liquid flow fields and relative motion between sludge particles and biogas bubbles. Then, a single granular sludge particle of various sizes was used in a 2D device at microscale for studying quantitatively the dynamical behavior of the complex anaerobic reactions under different hydrodynamic conditions. The image analysis techniques offer an opportunity to observe and quantify the nucleation and growth of biogas bubble at microscale on the sludge granule. In addition, the liquid flow fields were measured by a micro-PIV and the flow conditions were perfectly controlled in the microdevice. Finally, the role of hydrodynamic conditions on the biogas production efficiency at both micro- and mesoscale is discussed from these results.