Automatic buffer capacity model building for advanced interpretation of titration curves.

An automatic buffer capacity model building algorithm was developed. The objective of this algorithm is to characterize multiple buffer systems from experimental titration curves. Starting from a simple mathematical model that incorporates the available prior knowledge on the buffer system, the model is sequentially extended by incorporating additional monoprotic buffer equations.

Validation and implementation of model based control strategies at an industrial wastewater treatment plant.

In this paper, the practical implementation and validation of advanced control strategies, designed using model based techniques, at an industrial wastewater treatment plant is demonstrated. The plant under study is treating the wastewater of a large pharmaceutical production facility. The process characteristics of the wastewater treatment were quantified by means of tracer tests, intensive measurement campaigns and the use of on-line sensors.

Modelling of activated sludge acclimisation to a non-ionic surfactant.

A model is proposed to describe activated sludge acclimatisation to a non-ionic surfactant. The model was calibrated automatically, using WEST, a specific software environment for wastewater treatment model building, simulation and parameter estimation. The assays have been performed in a sequencing-batch reactor (SBR), using a non-ionic surfactant as sole carbon source and non-acclimatised sludge.

Modeling of a reactive primary clarifier.

Even though many models have been proposed for primary clarification, none is directly compatible with the ASM1. The objective of this paper is to present the development of a reactive primary clarifier model to be used in a wastewater treatment plant simulator (WEST). A model simulating COD behavior has been developed based on the Takacs model, and was tested with full-scale data.

An overview of the posters presented at Watermatex 2000. III: Model selection and calibration/optimal experimental design.

This paper presents an overview of the posters presented in sessions 7 and 8 of the Watermatex 2000 conference. These posters present two aspects of modelling biological processes--model selection and calibration. Special attention is given to the papers on OED (Optimal Experimental Design), which is a method of optimising the data collection for model selection and calibration.

An overview of the posters presented at Watermatex 2000. II. Sensor/monitoring, control and decision support systems.

This paper gives an overview of the poster sessions on sensor/monitoring, control and decision support systems, as they have been presented during the Watermatex 2000 conference. The COST benchmark for the comparison of different control strategies has been analysed. Two different teams have performed research on the control of sewers to decrease combined sewer overflows.

An overview of the posters presented at Watermatex 2000. I. New models/integrated urban wastewater systems/time series analysis.

This paper presents an overview of the posters presented in the sessions 1, 6 and 9 of the Watermatex 2000 conference. The first session focused on the development of new models in different areas of environmental technology, e.g.

Practical identifiability of model parameters by combined respirometric-titrimetric measurements.

An earlier study on theoretical identifiability of parameters for a two-step nitrification model showed that a unique estimation of the yield YA1 is possible with combined respirometric-titrimetric data, contrary to the case where only one type of measurement is available. Here, the practical identifiability of model parameters was investigated via evaluation of the output sensitivity functions and the corresponding Fisher Information Matrix (FIM). It appeared that the FIM was not sufficiently powerful to predict the practical identifiability of this case with combined measurements as parameters could indeed be identified despite the fact that the FIM became singular.

Identifiability and uncertainty analysis of the river water quality model no. 1 (RWQM1).

State of the art models as used in activated sludge modelling and recently proposed for river water quality modelling integrate the knowledge in a certain field. If applied to data from a specific site, such models are nearly always overparameterised. This raises the question of how many parameters can be fitted in a given context and how to find identifiable parameter subsets given the experimental layout.

Fast, simultaneous simulation of the integrated urban wastewater system using mechanistic surrogate models.

The urban wastewater system components (sewer, treatment plant, and river) are often modelled using complex mechanistic models. Mechanistic surrogate models are introduced here as simplified models that still contain some physical knowledge. Surrogate models are faster, but are less but still sufficiently accurate, and require more data to be calibrated.

Adequate model complexity for scenario analysis of VOC stripping in a trickling filter.

Two models describing the stripping of volatile organic contaminants (VOCs) in an industrial trickling filter system are developed. The aim of the models is to investigate the effect of different operating conditions (VOC loads and air flow rates) on the efficiency of VOC stripping and the resulting concentrations in the gas and liquid phases. The first model uses the same principles as the steady-state non-equilibrium activated sludge model Simple Treat, in combination with an existing biofilm model.

Development of a risk assessment based technique for design/retrofitting of WWTPs.

Up to now, within the design/retrofit of wastewater treatment plants (WWTPs), deterministic models were used to evaluate different scenarios on their merits in terms of effluent compliance. This paper describes an approach in which a Monte Carlo engine is coupled to a deterministic treatment plant model, followed by risk interpretation in the form of concentration-duration-frequency (cdf) curves of norm exceedance. The combination of probabilistic modelling techniques with the currently available deterministic models allows to determine the probability of exceeding the effluent limits of a WWTP.

Automatic buffer capacity model building for the purpose of water quality monitoring.

In this paper, buffer capacity profiles are used in the framework of automatic monitoring of water quality. The aim of the proposed methodology is to automatically and stepwise build buffer capacity models for each particular titrated sample, and to quantify the individual buffer systems that constitute the total buffer capacity. An automatic and robust model building algorithm has been developed and applied to many titration curves of effluent and river water samples.

GREAT-ER: a new tool for management and risk assessment of chemicals in river basins. Contribution to GREAT-ER #10.

The GREAT-ER (Geo-referenced Regional Exposure Assessment Tool for European Rivers) project team has developed and validated an accurate aquatic chemical exposure prediction tool for use within environmental risk assessment schemes. The software system GREAT-ER 1.0 calculates the distribution of predicted environmental concentrations (PECs) of consumer chemicals in surface waters, for individual river stretches as well as for entire catchments.

River Water Quality Model no. 1 (RWQM1): III. Biochemical submodel selection.

The new River Water Quality Model no. 1 introduced in the two accompanying papers by Shanahan et al. and Reichert et al.

River Water Quality Model no. 1 (RWQM1): II. Biochemical process equations.

In this paper, biochemical process equations are presented as a basis for water quality modelling in rivers under aerobic and anoxic conditions. These equations are not new, but they summarise parts of the development over the past 75 years. The primary goals of the presentation are to stimulate communication among modellers and field-oriented researchers of river water quality and of wastewater treatment, to facilitate practical application of river water quality modelling, and to encourage the use of elemental mass balances for the derivation of stoichiometric coefficients of biochemical transformation processes.

River Water Quality Model no. 1 (RWQM1): I. Modelling approach.

Successful river water quality modelling requires the specification of an appropriate model structure and process formulation. Both must be related to the compartment structure of running water ecosystems including their longitudinal, vertical, and lateral zonation patterns. Furthermore, the temporal variability of abiotic boundary conditions may be important and must be incorporated by an appropriate choice of model parameters.

Activated sludge monitoring with combined respirometric-titrimetric measurements.

A short review of different respirometric methods is presented, and advantages and disadvantages of different principles are discussed. In this study a combined respirometric-titrimetric set-up was applied to monitor the degradation processes during batch experiments with activated sludge. The respirometer consists of an open aerated vessel and a closed non-aerated respiration chamber.

New PEC definitions for river basins applicable to GIS-based environmental exposure assessment.

By means of GREAT-ER (Geo-Referenced Regional Exposure Assessment Tool for European Rivers) aquatic chemical fate simulations can be performed for river basins. To apply the resulting digital maps with local (river stretch specific) predicted concentrations in regional aquatic exposure and risk assessment, the output has to be aggregated to a (single) value representative of exposure in the catchment. Two spatially aggregated PEC definitions are proposed for this purpose: PECinitial (unweighted aggregation of concentrations just downstream of wastewater emissions) and PECcatchment (weighted aggregation of all average stretch concentrations).

On-line estimation of the maximum specific growth rate of nitrifiers in activated sludge systems.

The on-line estimation of the maximum specific growth rate of autotrophic biomass is addressed in this article. A general nitrification process model, which is valid for any realistic flow pattern, is used to develop the estimation algorithm. Depending on the measurements available, two estimation equations are derived.

A structured approach for selection among candidate metabolic network models and estimation of unknown stoichiometric coefficients.

A metabolic network model is one of the cornerstones of the emerging Metabolic Engineering methodology. In this article, special attention is therefore, given to the phase of model building. A five-stage structured approach to metabolic network modeling is introduced.

Kinetic characterization of mass transfer limited biodegradation of a low water soluble gas in batch experiments--necessity for multiresponse fitting.

A method was developed to characterize the kinetics of biodegradation of low water soluble gaseous compounds in batch experiments. The degradation of ethene by resting Mycobacterium E3 cells was used as a model system. The batch degradation data were recorded as the progress curve (i.

Validation of a metabolic network for Saccharomyces cerevisiae using mixed substrate studies.

Setting up a metabolic network model for respiratory growth of Saccharomyces cerevisiae requires the estimation of only two (energetic) stoichiometric parameters: (1) the operational PO ratio and (2) a growth-related maintenance factor k. It is shown, both theoretically and practically, how chemostat cultivations with different mixtures of two substrates allow unique values to be given to these unknowns of the proposed metabolic model. For the yeast and model considered, an effective PO ratio of 1.

Regulation of carbon metabolism in chemostat cultures of Saccharomyces cerevisiae grown on mixtures of glucose and ethanol.

Growth efficiency and regulation of key enzyme activities were studied in carbon- and energy-limited chemostat cultures of Saccharomyces cerevisiae grown on mixtures of glucose and ethanol at a fixed dilution rate. Biomass yields on substrate carbon and oxygen could be adequately described as the net result of growth on the single substrates. Activities of isocitrate lyase and malate synthase were not detected in cell-free extracts of glucose-limited cultures.

An activated sludge-based biosensor for rapid IC50 estimation and on-line toxicity monitoring.

The RODTOX (Rapid Oxygen Demand and TOXicity tester), an activated sludge-based respirographic biosensor, is a device for on-line monitoring of the short-term biochemical oxygen demand (stBOD) and potential toxicity of incoming wastewater on the basis of on-line interpretation of respirograms resulting from pulse additions of either calibration substrate or sample. The principle of toxicity detection is based on the comparison of calibration respirograms before and after receiving a potential toxicant. In this paper, the results of the RODTOX as an on-line toxicity monitor are presented.