Benchmark Simulation Model No 2 – General Protocol and Exploratory Case Studies U. Jeppsson 1 , M.-N. Pons 2 , I. Nopens 3 , J. Alex 4 , J.B. Copp 5 , K.V. Gernaey 6 , C. Rosen 1 , J.-P. Steyer 7 and P.A. Vanrolleghem 8 1 IEA, Lund University, Box 118, SE-221 00 Lund, Sweden (E-mail: ulf.jeppsson@iea.lth.se, christian.rosen@iea.lth.se) 2 LSGC-CNRS-ENSIC-INPL, 1 rue Grandville, BP 451, F-54001 Nancy cedex, France (E-mail: marie-noelle.pons@ensic.inpl-nancy.fr) 3 BIOMATH, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium (E-mail: ingmar.nopens@ugent.be) 4 ifak e.V. Magdeburg, Steinfeldstr. 3, D-39179 Barleben, Germany (E-mail: jens.alex@ifak.eu) 5 Primodal, Inc., 122 Leland Street, Hamilton, Ontario L8S 3A4, Canada (E-mail: copp@primodal.com) 6 Dept of Chemical Engineering, Technical University of Denmark, Building 229, DK-2800 Kgs. Lyngby, Denmark (E-mail: kvg@kt.dtu.dk) 7 INRA, UR050, Laboratoire de Biotechnologie de l’Environnement, Avenue des Etangs, Narbonne, F-11100, France (E-mail: steyer@ensam.inra.fr) 8 modelEAU, Dépt de génie civil, Université Laval, Québec, G1K 7P4, QC, Canada (E-mail: peter.vanrolleghem@gci.ulaval.ca) Abstract Over a decade ago, the concept of objectively evaluating the performance of control strategies by simulating them using a standard model implementation was introduced for activated sludge wastewater treatment plants. The resulting Benchmark Simulation Model No 1 (BSM1) has been the basis for a significant new development that is reported on here: Rather than only evaluating control strategies at the level of the activated sludge unit (bioreactors and secondary clarifier) the new BSM2 now allows the evaluation of control strategies at the level of the whole plant, including primary clarifier and sludge treatment with anaerobic sludge digestion. In this contribution, the decisions that have been made over the past three years regarding the models used within the BSM2 are presented and argued, with particular emphasis on the ADM1 description of the digester, the interfaces between activated sludge and digester models, the included temperature dependencies and the reject water storage. BSM2-implementations are now available in a wide range of simulation platforms and a ring test has verified their proper implementation, consistent with the BSM2 definition. This guarantees that users can focus on the control strategy evaluation rather than on modelling issues. Finally, for illustration, twelve simple operational strategies have been implemented in BSM2 and their performance evaluated. Results show that it is an interesting control engineering challenge to further improve the performance of the BSM2 plant (which is the whole idea behind benchmarking) and that integrated control (i.e. acting at different places in the whole plant) is certainly worthwhile to achieve overall improvement. Keywords Benchmarking; BSM2; control; evaluation criteria; simulation; wastewater treatment; whole plant modelling INTRODUCTION The Benchmark Simulation Model No 2 (BSM2) is a detailed protocol for implementing, analysing and evaluating the impact and performance of both existing and novel control strategies applied to wastewater treatment plants (WWTPs). The on-going research and development of BSM2 is being performed within the framework of the IWA Task Group on Benchmarking of Control Strategies for WWTPs , established in 2005 (see www.benchmarkwwtp.org). This Task Group (TG) is also developing an associated benchmark system that focuses on long-term monitoring performance