Abstract

A comparative study was undertaken of anaerobic continuous stirred tank reactors (CSTRs) at mesophilic (37°C) and thermophilic (55°C) temperatures. The reactors were operated at different HRT. The results showed that the longer HRT achieved better process stability as total volatile fatty acid (TVFA) levels and TVFA/alkalinity ratio gradually increased response to the lower HRT. At HRT of less than 6 days, the mesophilic reactor could not be operated while the thermophilic reactor worked satisfactorily. TCOD removal in thermophilic reactor was slightly lower (63.3-75.4%) than that in the mesophilic reactor (64.6-80.0%) when the HRT was tested almost to the point of digester failure. The experimental data were evaluated to determine the kinetic parameter of the process. The results achieved methane yield coefficient of 0.378 and 0.333-1 CH4/gTCODremoved and biomass yield coefficient of 0.263 and 0.284 gVSS/gTCOD for mesophilic and thermophilic reactors, respectively. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.