Influence of mixing rate on anaerobic digestion, biogas generation and CFD optimization

The significance of mixing in the anaerobic process for achieving optimal system efficiency and biogas generation was investigated. A continuously-stirred tank reactor was run with POME sludge and to make bacterial development, and operate at a mixing rate of 110 rpm. At the end of 60 days, the mixing rates were to 0 rpm, 55 rpm, and 195 rpm in every digester. Gas generation was monitored for a retention time of 20 days. The result revealed that reactor mixing rate was needed to be maintained for having a control on the anaerobic system. Furthermore, a higher amount of biogas was produced with a low mixing rate. Besides, it was noticeable that a mixing rate of 195 rpm resulted in a significant decrease in biogas generation. However, biogas generation was increased at a mixing rate of 55 rpm. A velocity gradient threshold was found above which increase of mixing rate reduces biogas production.