Anaerobic digestion of sewage sludge: macromolecular composition and IWA ADM1 application

The aim of this study is to characterize sewage sludge (a mixture of primary and secondary sludge) coming from an anaerobic digester (AD) in order to implement the IWA Anaerobic Digestion Model no°1 (ADM1, Batstone et al., 2002) and to simulate the process unit behaviour. In order to estimate parameters for the ADM1 implementation and understand sludge properties, the digester was monitored for two months. Traditional chemical-physical parameters and key macromolecular compounds for anaerobic biodegradability (such as carbohydrate, proteins, lipids and volatile fatty acids) were measured samples drawn at inflow and outflow. Biomethane potential (BMP) experiments were performed in triplicate on sewage sludge and digestate. Parameters collected were used to define the influent model input adopting an ASM1/ADM1 interface (Copp’s interface, Copp et al., 2003). BMP tests simulations were realized to calibrate the model, defining an operative procedure. Data set from monitoring period was used for model validation. The simulations underlined potential of AD modelling tool and the importance of macromolecular composition assessment for a correct COD’s fractions and stoichiometric parameters estimate.