Kinetics of poultry litter in a leach bed reactor with agitation based on two mechanisms: Enzymatic hydrolysis and direct solubilization

Two-phase anaerobic digestion including a hydrolyzer is considered necessary for solid waste treatment. In this study, a novel hydrolyzer with agitation was developed to treat poultry litter. Four experiments at temperature 35 °C were conducted under these conditions: 1200 and 800 g poultry litter with agitation (200 and 133 g L−1), and 800 and 400 g without agitation (133 and 67 g L−1). The experiments showed that agitation accelerated the hydrolytic rate of poultry litter, and the highest destruction of TS and VS was 92.4 and 91.9%, compared to 58.2 and 48.7% without agitation. Butyric acid and its isomers accounted for the highest equivalent COD among VFAs for all experiments. Two hydrolytic mechanisms were also identified, i.e., direct solubilization and enzymatic hydrolysis, and the corresponding kinetic model was developed. The rate constants determined by the model and the simulated kinetic curves indicated that direct solubilization was more significant than enzymatic hydrolysis under agitation, while the opposite was true without agitation. Use of agitation also reduced the time to reach stable concentrations under same substrate loading schemes.