Genomineerden Gijs Oskam prijs
Origin and behavior of particles in
drin-king water networks
ir Christian Kivit
Afstudeercommissie: prof.ir. J.C. van Dijk; prof.dr.ir. N. van de Giesen; ir. J.Q.J.C. Verberk; ir. J.H.G. Vreeburg.
Processes involved in the treatment of water for drinking water purposes are relatively well under-stood in comparison to processes in the drinking water networks. However, in the distribution network many unclaimed areas of research are still waiting to be discovered. This thesis focuses on processes in drinking water networks which infl uence the water quality. For this purpose data of particle counters have been analyzed by using a tool developed during this thesis called the ERF. This analysis shows the main contributors to the particle load of distribution networks: 1) peaks at the treatment plant and 2) corrosion of grey cast iron mains. This outcome is important information for the operation of treatment plants and water quality monitoring of the distribution network.
Particles in drinking water networks settle to form sediment, which caused discolored water and pro-vides a home for organic growth. In order to study the origin and behavior of particles, measurements were performed in three operational drinking water networks locations which were fed by different tre-atment processes: full fl ow ultra fi ltration, slow sand fi ltration and conventional treatment of groundwater. At each location the turbidity and particle concentra-tion were simultaneously monitored at three points: at the treatment plant, in a transport and distribution main. On-line measurements were executed for each network for a period of several weeks. The results show that behavior of particles such as sedimentation and resuspension, occur in all distri-bution mains and transport mains of limited dimen-sions. These processes cause an extra variation of the water quality. The extreme range factor (ERF), an analysis tool for monitoring the occurrence of sedimentation and resuspension developed during
ir. C.F.T. Kivit afgestudeerd aan de TU Delft,
thans werkzaam bij Kiwa
58e Vakantiecursus in Drinkwatervoorziening & 25e Vakantiecursus in Riolering en Afvalwaterbehandeling
this thesis, has been introduced and showed results in line with the hypothesis.
The main conclusion based on measurements in operational drinking water mains is that the main contributors to the amount of particles in the drinking water network are 1) peaks at the treatment plant, which can either be regular cycles or incidental peaks due to adjustments of the treatment process, and 2) corrosion of cast iron mains. Measurements show that the peaks at the treatment plant can contribute to more than half of the total particle load originating from the treatment plant. While the impact is signifi cant, the time period of these peaks is negligible and often the occurrence of these peaks is avoidable. Process management can assist in decreasing this particle load entering the drinking water network. On the other hand, corrosion of cast iron mains can seriously decrease the quality of water. If cast iron mains are present in the network, efforts to improve the water quality should in that case be focused on improving the drinking water distribution mains.
Looking at the measurement setup it can be con-cluded that including a particle counter gives more information on water quality changes, the origin of
water quality peaks and gives an accurate residence time over the course of 24 hours. The data is more precise and gives more information because of the large number of data streams.
The results of this study enhance the understanding of the origin and behavior of particles in drinking water networks and can be used to assist decisions made on and evaluation of measurements in the drinking water system.
Figure 1 - Comparison between regular daily particle load and three peak
