ADM1 calibration using BMP tests for modeling the effect of autohydrolysis pretreatment on the performance of continuous sludge digesters.

Improving anaerobic digestion of sewage sludge through pretreatment techniques is a suitable solution for better sludge management. In this sense, modeling may present itself as an important tool to assess and predict process performance and pretreatment effects. In this study, the feasibility of using biochemical methane potential (BMP) tests data for calibrating the Anaerobic Digestion Model No. 1 (ADM1) was evaluated, in order to simulate the operation of continuous digesters fed, at different HRTs, with raw and autohydrolysis-pretreated waste activated sludge. This was achieved using a simplified COD fractioning methodology proposed to define ADM1 inputs. Hydrolysis constant rates were determined as the most sensitive parameters, and estimated using BMP tests. The calibrated model was then cross-validated with continuous digesters data sets. Good model performance was attained employing these techniques. The ADM1 was able to successfully represent the consumption of slowly biodegradable organic matter in BMP tests, the changes in hydrolytic limiting steps due to the autohydrolysis pretreatment and the behavior of the continuous digesters in overall. The COD fractioning methodology and the Xc variable manipulation proposed seemed to be crucial for proper model predictions. Results indicate that BMP tests are a suitable data source for ADM1 calibration, and that the model can be a powerful tool to assess the effect of the autohydrolysis pretreatment on the anaerobic digestion of sewage waste activated sludge.