REAL-TIME MODELLING AND SIMULATION APPLIED TO THE TREATMENT OF ELECTROPLATING WASTEWATER Cécile NARCE, Konrad SZAFNICKI, Jacques BOURGOIS Ecole nationale supérieure des mines de St-Etienne 158, cours Fauriel F-42023 SAINT-ETIENNE Cedex 2 (France) e-mail : narce@emse.fr Phone: +33 4.77.42.02.20 Fax: +33 4.77.42.66.33 Abstract: Eco-industrial processes require high reliability control and supervision methodologies, so as to achieve the best compromise possible between the process’ efficiency, safety and economy. Industries often focus on the two first objectives mainly, since they are unwilling to “experiment” not yet validated and/or complex control methodologies if safety and/or efficiency of the process may be jeopardized. This work focuses on an industrial wastewater treatment process, including a cyanides oxidation stage and a neutralization stage, applied to the surface treatment effluents. The project involved the development and validation of a model which enables to simulate various pH-control strategies as well as faults in the CSTRs. Copyright  2002 IFAC Keywords: Environmental engineering, Water pollution, Industrial control, Modelling, Simulation, Diagnosis. 1. INTRODUCTION Metal processing activities (e.g. electroplating) use huge quantities of water during their manufacturing cycles. They thus generate significant amounts of wastewater, which usually do not satisfy environmental regulations so as to be rejected directly to the receiving water. These effluents, containing mainly heavy metals and cyanides, may be either strongly alkaline and/or very acidic. Therefore they have to be treated in a dedicated wastewater treatment plant, consisting of several physical-chemical stages (Degrémont Ed., 1991). The regulations, however, tend to be more and more strict and limitative as far as admissible quantities of rejected pollutants (metal ions, cyanides, …) are concerned (e.g. in the coming EU-regulations: Table 1). Moreover, several stages of the treatment process imply risks for the operators’ health and even for their life if not optimally controlled, Fig.1 (Szafnicki, et al., 1998). For example, chemical reactions implying cyanides may produce toxic (even lethal !) intermediary compounds, such as cyanogen chloride (CNCl) or hydrocyanic acid (HCN). The goal of this project is to develop and validate on industrial data a real-time model enabling a better understanding of the physical and chemical processes occurring in Continuously Stirred Tank Reactors (CSTR), in order to optimize their reliability, efficiency, economy, and safety of the treatment. Table 1 Rejection limitations (mg/L) Elements 1985 Future… Al Cr VI Cr III Cr total Cu Fe Ni Pb Zn CN - 5.0 0.1 3.0 3.0 2.0 5.0 5.0 1.0 5.0 0.1 5.0 0.1 … 0.5 0.5 5.0 0.5 0.5 2.0 0.1 Copyright © 2002 IFAC 15th Triennial World Congress, Barcelona, Spain