E. J. M. Blokker

Bio: E. J. M. Blokker is an academic researcher. The author has contributed to research in topics: Network model & Solver. The author has an hindex of 1, co-authored 1 publications receiving 21 citations.

Combining the Probabilistic Demand Model SIMDEUM With a Network Model

Abstract: Modeling of water quality in water distribution systems can be improved significantly when using stochastic demands. The stochastic demand pattern generator SIMDEUM is based on stochastic information on end users as retrieved from surveys. Stochastic demand patterns from SIMDEUM were applied in a small network model of 550 demand nodes in a residential area in the Netherlands. An EPANET based network solver was used to assess velocities and travel times. The actual measurements agree well with the simulations.

Discolouration in drinking water systems: a particular approach

Abstract: The quality of drinking water in the Netherlands meets high standards as is annually reported by the Ministry of Housing, Spatial Planning and the Environment (VROM)(Versteegh and Dik, 2006). Also the water companies themselves report in the voluntary Benchmark that water quality is one of the least discriminating factors as all the companies ‘comply generously’(VEWIN, 2004). Despite this reported high quality, water companies still report between 3000 and 6000 customer complaints about discolouration annually. The report on the Benchmark mentions that of all the parameters turbidity is causing most of the water quality failures. These figures are based on the data in the report system used to communicate the outcomes of the legal testing programme to the inspectorates (REWAB, 2004). The most common process associated with the phenomenon of discolouration is historically the corrosion of cast iron pipes as is suggested on the site of the Drinking Water Inspectorate in the UK (DWI, 2007). On many websites of Dutch water companies, however, particles originating during treatment are also identified as the source of deposits in the network. Many authors who studied the corrosion of cast iron in potable water systems conclude that this is a major cause of discolouration. (Smith et al., 1997; McNeill and Edwards, 2001). Recent studies (Prince et al., 2003) have suggested that more sources for particles besides from corrosion play a role in the discolouration problem. A large proportion of the customer contacts that drinking water supply companies across the world receive, stem from complaints on the occurrence of discoloured water in the drinking water distribution system (DWDS). Fig 1-1 shows a typical breakdown of customer contacts for a UK water company (Vreeburg and Boxall, 2007). Fig 1-2 shows some examples of discoloured water supplied to customers, that have led to the complaints.

Importance of demand modelling in network water quality models: a review

Abstract: Today, there is a growing interest in network water quality modelling. The water quality issues of interest relate to both dissolved and particulate substances. For dissolved substances the main interest is in residual chlorine and (microbiological) contaminant propagation; for particulate substances it is in sediment leading to discolouration. There is a strong influence of flows and velocities on transport, mixing, production and decay of these substances in the network. This imposes a different approach to demand modelling which is reviewed in this article. For the large diameter lines that comprise the transport portion of a typical municipal pipe system, a skeletonised network model with a top-down approach of demand pattern allocation, a hydraulic time step of 1 h, and a pure advection-reaction water quality model will usually suffice. For the smaller diameter lines that comprise the distribution portion of a municipal pipe system, an all-pipes network model with a bottom-up approach of demand pattern allocation, a hydraulic time step of 1 min or less, and a water quality model that considers dispersion and transients may be needed. Demand models that provide stochastic residential demands per individual home and on a one-second time scale are available. A stochastic demands based network water quality model needs to be developed and validated with field measurements. Such a model will be probabilistic in nature and will offer a new perspective for assessing water quality in the drinking water distribution system.

Velocity-based self-cleaning residential drinking water distribution systems

Abstract: Resuspension of accumulated particles in residential networks is the main cause for customers to complain to the water company about the water quality. Preventing the particles from accumulating in these networks can be achieved by high velocities in pipes. Adding this velocity criterion to the conventional design criteria leads to a branched lay out of distribution networks, that perform better with respect to water quality, continuity of supply and investment costs. In close cooperation with fire brigades the conventional fire flow requirements were challenged. Based on modern building codes, it proved possible to reduce the capacity of fire-hydrants to 8.3 l/s (30 m 3 /h) in newly built areas. Six years after the introduction of the velocity criterion the characteristics of the newly laid networks have changed resulting in smaller diameter pipes and reduced length of networks. The amount of 100/110 mm pipes have dropped from 55% of the total length to 45% of total length. The total investment costs for new networks have dropped by 20% in the Netherlands.