Simulation Study On Enhancing Methane Production In Anaerobic Digestion By Exogenous H₂ Stimulation

The target of “carbon neutral” operation of wastewater treatment plant revives the study on enhancing energy conversion of excess sludge. This study aims at stimulating methane(CH4) production and increasing methane content in the biogas by introducing exogenous H2 into the anaerobic digester. Meanwhile, by extending the ADM1 model, this study carried out mathematical modeling based on the experimental processes. Model parameters were calibrated and validated by comparing the predicted and measured results. Furthermore, model-based prediction was performed towards sceneries which are difficult to investigate through actual experiments, in order to improve the experimental study.Previous study has demonstrated that introducing exogenous H2 could significantly promote the CH4 production. Maintaining a high initial H2 partial pressure of 0.33 bar in the batch operated anaerobic digester would stimulate the upstream hydrogenesis and acetogenesis progress other than restrain it. Meanwhile, the experiments showed that H2 consumption was accelerated in the homoacetogenesis process under H2 pressure of 0.33 bar, which leaded to that the H2 consumption rate in the homoacetogenesis process was comparable to that in the autotrophic methane-producing process.Following the above experiments, this study applied mathematical simulation technique to get a deeper understanding of experimental results. The original ADM1 model was extended by adding new reaction processes and related parameters. Specifically, homoacetogenesis process was added into the ADM1 model and H2 pressure was added as a new variable. The extended model(HAs-ADM1) was input into the AQUASIM 2.0 software to build a platform for mathematical simulation. A simulation with default parameters was performed firstly, to investigate the match between the predicated and measured results. Then the model parameters were calibrated to get a high agreement between the prediction and the experimental results. After the calibration and validation, the expended model can be applied in predicting the results of other operating strategies.