Witteveen, Netherlands
Witteveen, Netherlands

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Benedetti L.,WaterWays | Langeveld J.,Technical University of Delft | Nieuwenhuijzen A.F.V.,Witteveen Bos | Jonge J.D.,Waterschap de Dommel | And 5 more authors.
Water Science and Technology | Year: 2013

This project aims at finding cost-efficient sets of measures to meet the Water Framework Directive (WFD) derived goals for the Dommel River (The Netherlands). Within the project, both acute and longterm impacts of the urban wastewater system on the chemical and ecological quality of the river are studied with a monitoring campaign in the urban wastewater system (wastewater treatment plant and sewers) and in the receiving surface water system. An integrated model, which proved to be a powerful tool to analyse the interactions within the integrated urban wastewater system, was first used to evaluate measures in the urban wastewater system using the existing infrastructure and new real-time control strategies. As the latter resulted to be beneficial but not sufficient, this paper investigated the use of additional infrastructural measures to improve the system cost-effectively and have it meet the Directive's goals. Finally, an uncertainty analysis was conducted to investigate the impact of uncertainty in the main model assumptions and model parameters on the performance robustness of the selected set of measures. Apart from some extreme worst-case scenarios, the proposed set of measures turned out to be sufficiently robust. Due to the substantial savings obtained with the results of this project, the pay-back time of the whole monitoring and modelling work proved to be less than 5 months. This illustrates the power of mathematical modelling for decision support in the context of complex urban water systems. © 2013 IWA Publishing.

Korff M.,Deltares | Korff M.,University of Cambridge | Mair R.J.,University of Cambridge | VanTol A.F.,Deltares | Kaalberg F.J.,Witteveen Bos
Geotechnical Aspects of Underground Construction in Soft Ground - Proceedings of the 7th International Symposium on Geotechnical Aspects of Underground Construction in Soft Ground | Year: 2012

This paper explores the influence of the piled foundation on the building response to excavation-induced deformations. The influence of the type of foundation, the position of positive and negative skin friction zones, and the flexibility of the piles is evaluated with respect to both horizontal and vertical soil deformations. Case histories from the Netherlands are included from Amsterdam (North South Line) and Rotterdam (a building adjacent to the Willemspoortunnel). Most of the buildings are founded on timber piles ranging in length from 12-17 m. Conclusions are drawn about the interaction between the piled building and the soil deformation. © 2012 Taylor & Francis Group.

Mortier H.,Combinatie Crommelijn | Delfgaauw S.,Witteveen Bos
Assessment, Upgrading and Refurbishment of Infrastructures | Year: 2013

In the city of Delft, the existing two track railway viaduct will be replaced by a 2,4 km four track railway tunnel. The tunnel runs through the historic city centre and replaces a railway flyover, which divides the town in two parts. The shallow tunnel is executed using a top down building sequence using diaphragm walls. The alignment of the tunnel is projected below two structures of historic value. One of these structures is a still functioning windmill, called The Rose, built in the 16th century. The other structure is a medieval tower, The Beguine Tower, which was part of the fortification wall that surrounded the city of Delft at that time. To pass below both structures with the tunnel works, two different execution methods were defined. Below both structures temporary reinforced concrete slabs were cast, and after hardening of these slabs the subjacent foundations were separated from the structures above, which - in the mean time - were taken over by an alternative foundation. Then, the historical buildings were moved in such a way, the diaphragm walls and future tunnel deck could be built at that location. Finally, both the mill and the tower were replaced back to their original location, but now on top of the new tunnel deck. Then, the top down construction process of the remaining tunnel works took place. The article will focus upon execution techniques, allowed deformation criteria and the design models applied.

Gil J.A.,RWTH Aachen | Dorgeloh E.,RWTH Aachen | van Lier J.B.,Technical University of Delft | van der Graaf J.H.J.M.,Witteveen Bos | Prats D.,University of Alicante
Desalination and Water Treatment | Year: 2012

This paper corresponds to the second part of a study aiming to establish the best conditions to start-up decentralised membrane bioreactors. The first part focused on the impact of different operational parameters on the start-up, whereas this second part aims to find a substitute for activated sludge to serve as initial inoculum. Both low powdered activated carbon addition and Alumin 7 (alkaline coagulant) demonstrated a low performance in terms of filterability and operation. In turn, ferrous chloride (FeCl2), due to its ability to coagulate soluble and colloidal matter, was able to create a cake layer composed of large coagulated particles acting as a prefilter. Additionally, the combination of wastewater plus FeCl2 allowing sufficient contact time before the filtration starts has demonstrated to be the best way to start-up decentralised membrane bioreactor using this additive. Eventhough some drawbacks are associated with its high acidity, i.e. low pH, high conductivity and low NH4 +-N removal, the excellent filterabilities observed and the possibility to create a cake layer from "zero-biomass" convert this additive as a possible substitute for activated sludge. This is supported by particle size distribution measurements suggesting that the negative effects of fine particles are outweighed by the possibility of creating a cake layer that impedes pore blocking. © 2012 Desalination Publications. All rights reserved.

Gil J.A.,Technical University of Delft | Krzeminski P.,Technical University of Delft | Van Lier J.B.,Technical University of Delft | Van Der Graaf J.H.J.M.,Witteveen Bos | And 5 more authors.
Filtration and Separation | Year: 2011

A major study undertaken by a number of institutions and a leading engineering consultancy has investigated factors affecting the performance in operation of membrane bioreactors in a variety of different industrial applications. One of the most common problems affecting the operation of industrial MBRs appears when the dissolved oxygen (DO) drops under certain threshold for long periods. Filterability measurements offer a powerful tool for operators and can provide useful information to monitor MBR performance and seek causes in case of a problem in operation. The substances cleaned from trucks in this tank cleaning location, for example juices, syrup, chocolate and lecithin, are categorized as food degree. Different foaming episodes have been noticed by operators due to these substances. These results suggest that both the particles released to the supernatant plus the excess of filamentous derived from a deficient DO concentration resulted in a loss of filterability.

Krzeminski P.,Technical University of Delft | Van Der Graaf J.H.J.M.,Witteveen Bos | Van Lier J.B.,Technical University of Delft
Water Science and Technology | Year: 2012

This paper provides an overview of current electric energy consumption of full-scale municipal MBR installations based on literature review and case studies. Energy requirements of several MBRs were linked to operational parameters and reactor performance. Total and specific energy consumption data were analysed on a long-term basis with special attention given to treated flow, design capacity, membrane area and effluent quality. The specific energy consumption of an MBR system is dependent on many factors, such as system design and layout, volume of treated flow, membrane utilization and operational strategy. Operation at optimal flow conditions results in a low specific energy consumption and energy efficient process. Energy consumption of membrane related modules was in the range of 0.5-0.7 kWh/m 3 and specific energy consumption for membrane aeration in flat sheet (FS) was 33-37% higher than in a hollow fibre (HF) system. Aeration is a major energy consumer, often exceeding 50% share of total energy consumption. In consequence, coarse bubble aeration applied for continuous membrane cleaning remains the main target for energy saving actions. Also, a certain potential for energy optimization without immediate danger of affecting the quality of the produced effluent was observed. © IWA Publishing 2012.

Lousada-Ferreira M.,Technical University of Delft | Moreau A.,Technical University of Delft | Van Lier J.B.,Technical University of Delft | Van Der Graaf J.H.J.M.,Witteveen Bos
Water Science and Technology | Year: 2011

Activated sludge quality is one of the major factors influencing flux decline in membrane bioreactors (MBRs). Sludge filterability is a recognized parameter to characterize the physical properties of activated sludge. Decrease in filterability is linked to a higher number of submicron particles. In our present research we studied whether particle counting techniques can be used to indicate deflocculation of the sludge suspended fraction to submicron particles, causing the aforementioned filterability decrease. A total number of 105 activated sludge samples were collected in four full scale municipal MBRs. Samples were tested for filterability and particle counting in the range 2-100 μm. In 88% of the membrane tank samples the filterability varied between good and poor, characterized by the ÄR20, being 0 <ΔR 20< 1. Filterability varied following the season of the year, stability of the MBR operation and recirculation ratio. The membrane tank filterability can be improved by applying low recirculation ratio between MBR tanks. The applied particle counting methodology generated reproducible and reliable results in the range 10-100 μm. Results show that differences in filterability cannot be explained by variations in particle size distribution in the range 10-100 μm. However, measurable deflocculation might be masked by the large numbers of particles present. Therefore, we cannot exclude the suspended particles as a possible source of submicron particles that are subsequently responsible for MBR sludge filterability deterioration. © IWA Publishing 2011.

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