Application of Anaerobic Digestion Model No. 1 for simulating anaerobic mesophilic sludge digestion Carlos Mendes ⇑ , Karla Esquerre, Luciano Matos Queiroz Federal University of Bahia, Salvador-Ba, Brazil article info Article history: Received 20 May 2014 Accepted 13 October 2014 Available online xxxx Keywords: Anaerobic Digestion Model No. 1 Simulation Sewage sludge Hydraulic retention time abstract Improving anaerobic digestion of sewage sludge by monitoring common indicators such as volatile fatty acids (VFAs), gas composition and pH is a suitable solution for better sludge management. Modeling is an important tool to assess and to predict process performance. The present study focuses on the application of the Anaerobic Digestion Model No. 1 (ADM1) to simulate the dynamic behavior of a reactor fed with sewage sludge under mesophilic conditions. Parametric sensitivity analysis is used to select the most sen- sitive ADM1 parameters for estimation using a numerical procedure while other parameters are applied without any modification to the original values presented in the ADM1 report. The results indicate that the ADM1 model after parameter estimation was able to predict the experimental results of effluent ace- tate, propionate, composites and biogas flows and pH with reasonable accuracy. The simulation of the effect of organic shock loading clearly showed that an organic shock loading rate above of 35 kg/m 3 day affects the performance of the reactor. The results demonstrate that simulations can be helpful to support decisions on predicting the anaerobic digestion process of sewage sludge. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Sludge is generated as a residue from the treatment of munici- pal wastewater. It contains mainly water, organic matter, nutri- ents, living organisms and some non-biodegradable particles (Wawrzynczyk, 2007). Anaerobic digestion has been proven to be one of the most efficient process technologies for stabilizing sludge and furthermore it produces methane as a form of fuel which may reduce treatment cost (Wang et al., 2013). A mesophilic tempera- ture regime, 25–40 °C, can be more attractive than a thermophilic temperature regime, mainly because of the lower energy require- ments. Nevertheless, the heat required by thermophilic processes can be balanced with faster kinetics and increased methane gener- ation, resulting in a similar (or higher) net energy outcome. Anaerobic digestion of sludge may be highly affected by the spe- cific characteristics of the feed substrate, operational parameters such as hydraulic retention time (HRT) and organic loading rate, and environmental factors such as pH, presence of inhibitory or toxic substances, temperature and reactor configuration. Volatile fatty acids (VFAs), gas composition and pH are useful indicators for monitor- ing gradual changes in sludge treatment processes (Wang et al., 1997). Modeling is an important tool for assessing aspects of bioprocess- es, process design, determination of optimal operating conditions and controlling the anaerobic digestion processes. They improve the understanding of the system, the formulation and validation of hypothesis and are able to predict the system’s performance (Donoso-Bravo et al., 2011). Fundamental models describing anaer- obic digestion process have been developed in recent decades (Pavlostathis and Gossett, 1986; Siegrist et al., 1993; Kalyuzhnyi, 1997; Angelidaki et al., 1999; Siegrist et al., 2002; Dalmau et al., 2010; Gavala et al., 2003; Mu et al., 2008; Tartakovsky et al., 2008; Lee et al., 2009; Mairet et al., 2011; Muha et al., 2012). A specialist group working on anaerobic digestion for the Inter- national Water Association have been trying to condense all this knowledge into a model known as Anaerobic Digestion Model N1 (ADM1) which has been successfully applied to simulate the anaer- obic digestion of sewage sludge (Batstone et al., 2002; Blumensaat and Keller, 2005; Galí et al., 2009; Mairet et al., 2011). The aim of this research is to apply the ADM1 model to simulate the dynamic behavior of a reactor fed with sludge and simulate the application of organic shock loads under mesophilic conditions. 2. Materials and methods 2.1. Experimental data The investigation was carried out using a set of data derived from experiments conducted by Siegrist et al. (2002). Two anaero- bic rectors in lab-scale (28 L liquid volume, 5 L headspace) were http://dx.doi.org/10.1016/j.wasman.2014.10.013 0956-053X/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: carllosmendez@gmail.com (C. Mendes), karlaesquerre@ufba.br (K. Esquerre), lmqueiroz@ufba.br (L. Matos Queiroz). Waste Management xxx (2014) xxx–xxx Contents lists available at ScienceDirect Waste Management journal homepage: www.elsevier.com/locate/wasman Please cite this article in press as: Mendes, C., et al. Application of Anaerobic Digestion Model No. 1 for simulating anaerobic mesophilic sludge digestion. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.10.013