Kinetics study of methane production from anaerobic digestion of sludge and wastewater recycled pulp and paper

Abstract

Abstract Methane yield is one of the important factors that indicate the anaerobic digestion (AD) process efficiency. The AD is an available treatment of recycled pulp and paper sludge (RPPS) and recycled pulp and paper wastewater (RPPW). This process protects the environment and produces methane, which is considered as renewable energy. In this study, the anaerobic treatment of the RPPW and RPPS were studied using 1L completely stirred tank reactor (CSTR) at laboratory scale with mesophilic conditions. However, a kinetic study was carried out using four models in order to compare and adjust the experimental results. The experimental results show that the RPPW and RPPS methane productions were between 691 and 945 mL/g based on volatile solid (VS), and the corresponding digestion time was about 26 days for the both experiment. The corresponding digestion time could be understood through the methane production kinetic models by digestion experiments within a short time. Different kinetics models were tested including Richards, Logistic, modified Gompertz and Cone models. The obtained results show the modified Gompertz model as the suitable model since it gives the lowest deviation from experimental results. Therefore, the proposed model could be used to accurately predict behavior of AD processes.