Modification and calibration of anaerobic digestion model 1 to simulate volatile fatty acids production during fermentation of municipal sludge

Abstract

The present study modified the anaerobic digestion model No.1 (ADM1) to simulate biological volatile fatty acids (VFA) production from municipal sludge. A variable and constant stoichiometric approach was used to modify the ADM1. The model was implemented in the AQUASIM 2.0 modeling platform and calibrated with experimental data from the bench-scale semi-continuous flow acid fermenters to assess the model's performance in simulating the VFA generation under different operating conditions. After parameter estimation, the modified ADM1 simulated experimental results of acetic, propionic, and butyric acids with reasonable accuracy and goodness of fit values ranging from 0.90 to 0.99. The model validation using an independent data set from the calibration data successfully simulated propionic (goodness of fit of 0.89) and butyric acids (goodness of fit of 0.88) but underestimated acetic acid production (goodness of fit of 0.73). The presented results extend the applicability of the ADM1 to simulate VFA during anaerobic fermentation.