Application of the ADM1 model to advanced anaerobic digestion Wayne J. Parker * Department of Civil Engineering, University of Waterloo, Waterloo, Ont., Canada N2L 3G1 Received 20 November 2003; received in revised form 3 January 2005; accepted 5 January 2005 Available online 8 March 2005 Abstract In this paper the ADM1 model that has been developed by the IWA Task Group for Mathematical Modelling of Anaerobic Digestion Processes is summarized. The model was applied to a variety of anaerobic digestion scenarios that are presented in the literature and for each data set the model predictions were compared to experimental values. Based upon the model applications it was apparent that for accurate model simulations the influent sludge should be well characterized in terms of biodegradable and recalcitrant COD and also nitrogenous compounds. In almost all cases the model was able to reflect the trends that were observed in the experimental data however the concentrations of VFAs were consistently over-predicted in digesters with short SRTs. It would appear that the inhibition functions associated with low pH values tend to overestimate the impact of pH on bioki- netic rates for the acid-consuming bacteria. Application of the model with flow through of active biomass between digesters in series in temperature-phased systems needs to be further evaluated in the future. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Anaerobic digestion; Two-phase; Temperature-phased; Mesophilic; Thermophilic; Model; Sludge 1. Introduction Owners and operators of wastewater treatment plants are increasingly considering the use of advanced digestion technologies for producing pathogen-free bio- solids and for enhancing sludge stabilization. Some examples of such technologies include staged thermo- philic (Krugel et al., 1998), temperature-phased (TPAD) (Han et al., 1997), two-phase (Ghosh, 1987) and three- phase digestion (Drury et al., 2002). With the increasing complexity of these processes it is difficult to evaluate the impact of all process variables on the performance of the digesters. Hence, it is difficult to optimize the design and operation of these processes. Pilot testing for the purposes of optimization is challenging due to the extended time periods that are required to operate these processes. Given these factors, the use of models for predicting process performance over a range of design and operating conditions becomes attractive. Over the years a range of models have been develo- ped for modeling anaerobic digestion processes. Early models were steady state and assumed a rate-limiting step (Lawrence, 1971). However, the increasing com- plexity of the advanced digestion technologies requires more complex models that can represent the impacts of changing environments on chemical and microbial species. Based on reports in the literature there is evi- dence of a number of multi-species models that are based upon differing assumptions and have differing configurations (Angelidaki et al., 1999; Pavlostathis and Gossett, 1986; Siegrist et al., 1993). Relatively re- cently there has been a move by the International Water AssociationÕs (IWA) Task Group for Mathematical Modelling of Anaerobic Digestion Processes to develop a common model that can be used by researchers and practitioners (IWA, 2002). This model (ADM1) has a 0960-8524/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2005.01.022 * Tel.: +1 519 888 4567x6324; fax: +1 519 888 4349. E-mail address: wjparker@uwaterloo.ca Bioresource Technology 96 (2005) 1832–1842