IMPLEMENTATION OF ANAEROBIC DIGESTION MODELS FOR PLANT WIDE MODELING AND PERFORMANCE BENCHMARKING Usama Zaher*, Monica de Gracia** and Peter A. Vanrolleghem* * BIOMATH, Department of Applied Mathematics, Biometrics and Process Control,Ghent University, Coupure Links 653, B-9000 Gent - BELGIUM,(E-mail: usama.zaher@biomath.rug.ac.be, Peter.Vanrolleghem@rug.ac.be) ** CEIT- Environmental Engineering Unit, Paseo de Manuel Lardizabal,15. 20018 San Sebastián-Spain. Abstract Integration of Anaerobic Digestion Model (ADM) with the standard Activated Sludge Models (ASMs) is introduced for plant wide application. A flexible methodology is presented through an example in which the standard benchmark model of activated sludge systems is extended with an anaerobic digestion unit. To simulate the practice of sludge treatment in this example, two process units are added and configured to act as thickener and centrifuge before and after digestion respectively. To increase flexibility for further application two interfaces between activated sludge and digester model components are created. The structure of the transformers is briefly described. Results of the benchmark simulation are shown to highlight the effect of supernatant recycling. Keywords Anaerobic Digestion Models; Activated Sludge Models; Benchmark; Simulation INTRODUCTION Anaerobic digestion has a growing concern in the field of wastewater treatment. It is a cost effective process since it recovers energy, produce less sludge…etc. To avoid instability of the process, effective operating system is required. Thus, projects such as the EU TELEMAC project apply considerable effort to develop new sensors and effective control systems. The process is suitable for high load situations COD/VSS. However, it has limitations on the expected effluent quality in terms of SS, COD and more so, ammonia and phosphorus. Thus it needs post-treatment. A simulation benchmark can be used to evaluate the desired control systems, sensors and combination with other treatment processes. Therefore in this paper, a methodology is developed to extend a standard benchmark of activated sludge systems by inclusion of an anaerobic digestion unit. METHODOLOGY The Siegrist ADM has been chosen for illustration in this paper (Siegrist et al, 1995, 1993 & 1990). All modeling and simulation was performed in the WEST software (Hemmis nv, Kortrijk, Belgium) – (Vanhooren et al, 2002), using the Model Specification Language, MSL (Vangheluwe, 2000). Two transformers has to be developed for connecting the ADM with ASM1 (IWA, 2000) or vice versa. ASM1 to Siegrist ADM transformer Soluble components: - Hydrogen and methane are zeros, they are not expected in the aerobic effluent. - Knowing the pH CO 2 and HCO 3 - can be estimated from equilibrium. - Substrate is reduced to compensate for the depletion of the remaining dissolved oxygen and nitrates. The remainder will be split into acetate, propionate, amino acids and sugar, and Fatty acids according to predefined ratios (hydrolysis is not considered in this ADM). - Inerts will be passed through as such.