A. W. C. van der Helm

Modeling of Ozonation for Dissolved Ozone Dosing

Experimental research was carried out for calibration and validation of a model describing ozone decay and ozone exposure (CT), decrease in UV absorbance at 254 nm (UVA254), increase in assimilable organic carbon concentration and bromate formation. The model proved to be able to predict these parameters on the basis of the applied ozone dosage. The experimental ozone dosages ranged from 0.4 mg-O3/L to 0.9 mg-O3/L for natural water with a dissolved organic carbon concentration of 2.4 mg-C/L. The UVA254 was found to be an effective parameter for estimation of rapid ozone decay for natural water under experimental conditions tested. The experimental setup consisted of a bench-scale plug flow reactor (approximately 100 L/h) with dissolved ozone dosing.

Good modelling practice in drinking water treatment, applied to Weesperkarspel plant of Waternet

Good modelling practice increases the credibility and impact of the information and insight that modelling aims to generate. It is known to be crucial for model acceptance and it is a necessity to amass a long-term, systematic thorough knowledge base for both science and decision making. This paper shows how ten steps in model development and evaluation can also be applied to numerical modelling of drinking water treatment, using models of drinking water treatment processes of the Weesperkarspel treatment plant of Waternet. The Weesperkarspel plant consists of ozonation, pellet softening, biological activated carbon filtration and slow sand filtration. For the different processes models were developed that were used for operational improvements. The modelling resulted in new insights and knowledge about the treatment processes and improved operation of the processes. From scenario studies for the pellet softening it was concluded that chemical dosing can be diminished when by-pass ratio is increased and that pellet size can be controlled by measuring the difference in pressure guaranteeing fluidisation of the pellet bed. In addition, ozone dosage can be optimised by modelling ozone exposure, bromate formation and biologically degradable natural organic matter (NOM) under varying influent water quality.

Use of on-line UV/Vis-spectrometry in the measurement of dissolved ozone and AOC concentrations in drinking water treatment.

The concentrations of dissolved ozone and assimilable organic carbon (AOC) are important performance parameters in drinking water production. For the measurement of ozone, a spectral algorithm was developed that allows quantification in situ using a UV/Vis spectrometer probe. Furthermore, a strong correlation between the change in the absorption spectrum after individual treatment steps and the formation or removal of AOC in that treatment step was observed. This allowed the development of a spectral algorithm that predicts AOC formation during ozonation and subsequent removal in further treatment steps. This method has been verified at one pilot plant of the Amsterdam drinking water supply.

On-line monitoring of ozonation through estimation of Ct value, bromate and AOC formation with UV/Vis spectrometry

The application of ozone in water treatment serves many purposes, such as disinfection and degradation of organic micro-pollutants. To optimise the applied ozone dosage by on-line control, real-time information on the actual Ct value, the bromate and assimilable organic carbon concentration (AOC) is necessary. With UV/Vis spectroscopy, algorithms have been developed for the on-line determination of the Ct-value and the formation of bromate and AOC during ozonation. It was shown that these algorithms allow for the calculation of the optimal ozone dosage and provide a reliable indication of the amount of bromate and AOC formed during ozonation.

Explorascope: stimulation of language and communicative skills of multiple handicapped children through an interactive, adaptive educational toy

Abstract Very young non- or hardly-speaking children with severe disabilities need active guidance to stimulate interaction with their environment in order to develop their communicative and linguistic skills. Augmentative and alternative communication (AAC) systems can help this process, provided that they are tuned to this specific user group. LinguaBytes is a research programme, which aims at developing an interactive and adaptive educational toy that stimulates the language and communicative skills of multiple-handicapped children with a developmental age of 1–4 years. In this article we show which guidelines we consider essential for developing this tool. We have developed several concepts based on these guidelines, of which we elucidate Explorascope (E-scope). E-scope consists of a tangible toy-like interface that is adaptable to an individual child with respect to his or her cognitive, linguistic, emotional and perceptual-motor skills. A first user test shows that E-scope is promising and useful for this user group.