Kinetic analysis of anaerobic digestion of cattail by rumen microbes in a modified UASB reactor

The kinetics of anaerobic digestion of cattail by rumen microbes in a modified upflow anaerobic sludge blanket (UASB) reactor was systematically analyzed in this study. The Monod and first-order equations were combined to develop kinetic models to describe the substrate degradation, microbial growth and product formation. At an influent cattail concentration (volatile solids) of 12.1 g/L, hydraulic retention time of 0.75 day and solids retention time of 1.0–4.0 days, the concentration of reducing sugars was negligible, compared to the hydrolyzed cattail, indicating that the lignocellulosic hydrolysis was the rate-limiting step in the fermentation. The rate constant (k) of cattail degradation, true microbial growth yield (YEG) and the maintenance coefficient (m) were calculated as 1.50 day−1, 0.11 g/g and 0.103 g/(g h), respectively. The measured and estimated substrate degradation, microbial growth and product formation were in good agreement.