A systematic procedure for selecting identifiable parameter subsets for a given set of measured outputs is proposed. The aim is to only select those parameters which can be estimated uniquely from the dataset used. The proposed procedure consists of first selecting a reduced set of most sensitive parameters by sensitivity analysis and subsequently selecting identifiable parameter subsets using the Fisher information matrix. For a particular set of outputs obtained from a typical calibration exercise at a carrousel-type nitrogen removal plant, parameter subsets ranging from two to eight parameters were selected by this procedure. The procedure proved successful as the parameter subsets thus selected could be estimated accurately from simulated data without and with noise as well as from real data. However, the procedure is based on a property which is local in parameter space. Consequently, as an a priori assumption on the parameter vales has to be made at the start of the procedure, the selection results might be different from the results which would have been obtained by using the a posteriori parameter values. Hence, the sensitivity towards this a priori assumption was tested explicitly. For this purpose, the parameter space was sampled according to a Latin hypercube sampling scheme and the selection procedure was applied in all sampling points as if these were a priori estimates. From this extensive study it could be concluded that the results of the procedure were not too severely influenced by the a priori assumption on the parameter values. Therefore, the proposed procedure appears to be a powerful and practical tool for efficient and reliable model calibration.

A methodology for calibration of the activated sludge plant models is proposed on the basis of consolidated engineering experience and a scientific approach. According to the method, the definition of the target(s) plays a crucial role in the selection of the steps incorporated in this so-called 'Biomath-Calibration' protocol. For the activated sludge modelers this protocol tries to combine and link the state of the art methodologies for calibration of different processes in a wastewater treatment plant (hydraulics, biological reactions, sedimentation processes, etc.), and it can thus be used as a complete guideline for extensive model calibration tasks. Finally, an application of the methodology is presented in a case study for a nutrient removing oxidation ditch system.

The KALLISTO project aims at finding cost-efficient sets of measures to meet the Water Framework Directive (WFD) derived goals for the river Dommel. Within the project, both acute and long term impacts of the urban wastewater system on the chemical and ecological quality of the river are studied with an integral monitoring campaign in the urban wastewater system (WWTP and sewers) and in the river. Based on this monitoring campaign, detailed models were calibrated. These models are partly simplified and integrated in a single model, which is validated using the detailed submodels. The integrated model was used to study the potential for impact-based real-time control (RTC). Impact based RTC proved to be able to improve the quality of the receiving waters significantly, although additional measures remain necessary to be able to meet the WFD requirements

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Interactions between fluorescent horse heart cytochrome c derivatives (e. g. porphyrin cytochrome c and Znporphyrin cytochrome c) with surfactant interfaces in reversed micellar solutions have been studied, using different spectroscopic techniques. Anionic [sodium bis(2-ethylhexyl)sulfosuccinate, AOT] and cationic (cetyltrimethylammonium bromide, CTAB) surfactant solutions have been used in order to investigate the effects of charge interactions between proteins and interfaces.Circular dichroism reveals that much of the protein secondary structure is lost in AOT-reversed micelles, especially when the molar water/surfactant ratio, wo, is high (w, = 40), whereas in CTAB-reversed micelles secondary structure seems to be preserved.Time-resolved fluorescence measurements of the porphyrin in the cytochrome c molecule yields information about the changes in structure and the dynamics of the protein upon interaction with surfactant assemblies both in aqueous and in hydrocarbon solutions. With AOT as surfactant a strong interaction between protein and interface can be observed. The effects found in aqueous AOT solution are of the same kind as in hydrocarbon solution. In the CTAB systems the interactions between protein and surfactant are much less pronounced. The measured effects on the fluorescence properties of the proteins are different in aqueous and hydrocarbon solutions.In general, the observations can be explained by an electrostatic attraction between the overall positively charged protein molecules and the anionic AOT interface. Electrostatic attraction can also occur between the cytochrome c derivatives and CTAB because there is a negatively charged zone on the surface of the proteins. From the fluorescence anisotropy decays it can be concluded that in the CTAB-reversed micellar system these interactions are not important, whereas in an aqueous CTAB solution the proteins interact with surfactant molecules.Surfactant assemblies in organic media, called reversed micelles or, more general, water-in-oil microemulsions, have been investigated extensively over the past years. Many studies have been carried out towards the elucidation of structure and dynamics of reversed micelles [I -41 but also on the (bio)chemical and (bio)technological applications of these systems [2, 3, 5-91. In our laboratory an important line of research consists of the incorporation of proteins in reversed micelles in order to perform bioconversions of apolar compounds or to isolate proteins [lo -121. At present, the effects of protein solubilization on both protein and micelle structure and dynamics are not very clear. Because reversed micellar solutions are optically transparent, spectroscopic and ultracentrifugation techniques can be applied to study these effects. Several systems have been the subject of this kind of investigation, some containing cytoplasmatic, others containing membrane proteins [5, 7-91. Horse heart cytochrome c is a protein which in vivo is strongly associated via electrostatic interactions with the inner Correspo...