Kinetic evaluation of palm oil mill effluent digestion in a high rate up-flow anaerobic sludge fixed film bioreactor

A kinetic study of the anaerobic digestion process of palm oil mill effluent (POME) was carried out in a laboratory-scale up-flow anaerobic sludge fixed film (UASFF) bioreactor at mesophilic temperature (38 °C). Influent COD concentrations in the range of 5260–34725 mg/l were applied at steady state conditions. Chen and Hashimoto kinetic equation and a simplified Monod's model was employed to describe kinetics of POME anaerobic digestion at organic loading rates in the range of 0.88–34.73 g COD/l day. The hydraulic retention times (HRT) ranged between 1 and 6 days. Throughout the experiment, the removal efficiency of COD was between 80.6 and 98.6%. The methane production rate was between 0.287 and 0.348 l CH 4/g COD removed day. Biokinetic coefficients; apparent half-velocity constant, A, half-velocity constant, K s, maximum specific microbial growth rate, μ m, methane yield constant, Y M, and growth yield constant, Y x, were evaluated. The apparent rate constants, K, calculated by simplified Monod model were in the range of 2.9–7.4 l CH 4/g COD day. At different influent COD concentrations, K values showed a linear relationship with variations of VSS content of the reactor.