Modeling particle transport and discoloration risk in drinking water distribution networks

Abstract

Abstract. Discoloration of drinking water is a worldwide phenomenon caused by accumulation and subsequent remobilization of particulate matter in drinking water distribution systems (DWDSs). It contributes a substantial fraction of customer complaints to water utilities. Accurate discoloration risk predictions could improve system operation by allowing for more effective programs on cleaning and prevention actions and field measurements, but are challenged by incomplete understanding on the origins and properties of particles and a complex and not fully understood interplay of processes in distribution networks. In this paper, we assess and describe relevant hydraulic processes that govern particle transport in turbulent pipe flow, including gravitational settling, bedload transport, and particle entrainment into suspension. We assess which transport mechanisms are dominant for a range of bulk flow velocities, particle diameters, and particle mass densities, which includes common conditions for DWDSs in the Netherlands, the UK, and Australia. Our analysis shows that the theoretically predicted particle settling velocity and threshold shear stresses for incipient particle motion are in the same range as, but more variable than, previous estimates from lab experiments, field measurements, and modeling. The presented material will be used in the future development of a numerical modeling tool to determine and predict the spatial distribution of particulate material and discoloration risk in DWDSs. Our approach is aimed at understanding specific causalities and processes, which can complement data-driven approaches.

Dynamic Hydraulics in a Drinking Water Distribution System Influence Suspended Particles and Turbidity, But Not Microbiology

“…Husband et al [6,23] showed with laboratory experiments and on-site studies that increasing shear stress results in the mobilization of different cohesive layers of accumulated material in the pipes, mobilizing particles from different sizes and composition. The particle behavior can vary between DWDSs with different water quality and pipe materials, as shown by van Summeren and Blokker [7] with a modelling study based on sediment collected in the United Kingdom, in the Netherlands, and in Australia with different particle sizes and densities. Even within the same DWDS supplying water from a single water source, the composition of deposits or suspended particles can vary as a result of microbial activity [24] or inorganic composition (e.g., as a result of corrosion) [22].…”

“…The complex hydraulic conditions resulting from the system configuration and varying water consumption have a direct impact on water quality. Turbidity, for example, is directly influenced by flow velocity variations impacting particle deposition and resuspension, as well as shear stress on pipe walls [4,6,7]. The impact of varying flow velocities on microbial parameters in the drinking water is, however, less understood.…”

Optimal design-for-control of self-cleaning water distribution networks using a convex multi-start algorithm

“…Central to their findings was the role of diurnal flow velocities on particle transport and fate. This connection between discolouration and hydrodynamic conditions has been supported by numerous experimental and theoretical studies; see van Summeren and Blokker (2017) and Armand et al (2018) for reviews on the topic. These studies have mainly focused on the development of predictive tools for modelling particle transport and accumulation processes.…”

“…Because such tools require extensive field testing and are generally limited to pipe-level assessments, their use in practice has not yet been widespread. Recognizing this limitation, van Summeren and Blokker (2017) presented a theoretical particle transport model, combining the effects of gravitational settling, hydraulic shear stresses, and bed-load transport. To complement this, several laboratory-based experimental studies have emerged to better understand the complex interactions between particle properties and pipe hydraulics (e.g.…”

Public Attitudes towards Digital Water Meters for Households

“…Dutch households are relatively water efficient compared to other industrialised countries [61]. More recently, however, the frequency and length of heatwaves have substantially increased, leading to environmental degradation [62], lower pressure, sometimes discolouration at the tap [63,64], and freshwater resources-particularly groundwater resources-are under pressure [65],. These developments are paving the way for the smallscale introduction of DWM as a means to enhance domestic water conservation.…”