In-Storage-Psychrophilic-Anaerobic-Digestion (ISPAD) process. Part II: Model Validation

Abstract

In-Storage-Psychrophilic-Anaerobic-Digestion (ISPAD) is a sequentially fed batch treatment system operating at a temperature fluctuating with that of ambient. Because of its specific operation modes and the acclimation of its microbial groups, its microbial kinetics were determined from laboratory data, and a specific mathematical model was developed to simulate its process and to optimize its management. The objective of this study is therefore to validate this ISPAD model using further laboratory data obtained from batch tests conducted in flasks. For this purpose, glucose at 630 mg/L, was fed to 8-year-old ISPAD inoculum and digested at 18 °C. Changes in glucose, VFAs and pH were monitored along with biogas production. The cross-validated coefficient of determination () was used to determine the fit between the model prediction and the experimental values. The ISPAD model was able to strongly predict glucose degradation, VFAs, pH, and methane. However, the model weakly predicted the early CO₂ changes over time, likely because of its water solubility.