Simulation of Two-Stage Anaerobic Digestion Using Extended ADM1 Mode

The aim of this study was to build a competent process model for the simulation of different forms of a two-stage anaerobic digestion systems that can support previous experimental studies conducted on anaerobic two-stage digestion of sewage sludge. The MATLAB model is a modification of the single-stage extended ADM1 model, built in a previous study by Zhang et al, to simulate a two stage anaerobic digestion system. The modified ADM1 model was implemented for batch-fed and continuous mode systems and the efficiency of the model was evaluated. The model was also tested for 4 configurations based on the thermophilic and mesophilic temperature ranges and the most effective configuration was ascertained for the batch-fed and continuous mode scenarios. The simulation of the thermophilic and mesophilic conditions was performed through the estimation of the appropriate parameters for each temperature condition from literature and by the use of a manual parameter estimation method for the identification of the most sensitive parameters. The accuracy of the model was then evaluated by comparison with experimental results provided in literature. The model was able to predict the dynamic behavior of two-stage digestion process reasonably well and the simulation results agreed fine with the two-stage reaction process described in previous literature. The model enabled the possible identification of the optimum operating conditions for both the batch--fed and continuous mode two-stage anaerobic bioreactor systems.