The process of model building and simulation of ill-defined systems: Application to wastewater treatment

In recent years, there has been a growing awareness of the ill-defined natu re of environmental processes. To provide a frame of reference for discussi ons regarding ill-defined systems, a taxonomy and terminology of the modell ing and simulation of systems is presented. Due to the complexity of ill-de fined systems, it is not only necessary to describe the nature of models, b ut also to describe modelling procedures. This enables the modeller to obta in the model which best fits his goals (optimal model). For meaningful desc ription of models, different model formalisms will be presented. Furthermor e, modelling procedures will be described at a generic level and different model formalisms will be presented. Throughout this paper, Waste-Water Trea tment Plants and processes occurring within these plants will illustrate th e definitions given.