The Self-Cleaning Velocity in Practice

Blokker, Mirjam; Vreeburg, J.H.G.; Schaap, Peter G.; Dijk, J. C. van

doi:10.1061/41203(425)19

Cited by 33 publications

(40 citation statements)

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“…Our analysis shows that for common DWDS conditions, a large range of settling velocities u s , and shear stress thresholds for incipient motion, θ c , and resuspension, θ rs , can be expected, because of the strong sensitivity to the average bulk flow velocityū f , particle diameter, d p , and density, ρ p . The theoretical model predicts u s , θ c , and θ rs values that are compatible with previously determined values of θ c and θ rs (or their velocity counterparts) and u s that were derived from field measurements and modeling for Dutch DWDSs Blokker et al, 2010) or lab experiments with drinking water from Australian utilities (Ryan et al, 2008). However, a model that takes into account these dependencies is expected to result in a more comprehensive and generically applicable model to determine particle accumulation.…”

Section: Outlook and Concluding Remarkssupporting

confidence: 51%

Modeling particle transport and discoloration risk in drinking water distribution networks

Summeren

Blokker

2017

Drink. Water Eng. Sci.

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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.

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Section: Outlook and Concluding Remarkssupporting

confidence: 51%

Modeling particle transport and discoloration risk in drinking water distribution networks

Summeren

Blokker

2017

Drink. Water Eng. Sci.

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“…Discolouration material clearly does build up in the trunk mains observed in this paper, this is despite the relatively high velocity percentiles shown in Table 1 that vastly exceed the 'self-cleaning' velocity ranges (0.25 m/s-0.4 m/s) associated with smaller distribution pipes [3,28]. This agrees with the findings of other authors conducted on large diameter pipes (i.e., over 200 mm), which find no evidence for self-cleaning velocities or shear stresses [18,24,29].…”

Section: Discussionmentioning

confidence: 68%

Data-Driven Study of Discolouration Material Mobilisation in Trunk Mains

Meyers

Kapelan

Keedwell

2017

Water

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Abstract:It has been shown that sufficiently high velocities can cause the mobilisation of discolouration material in water distribution systems. However, how much typical hydraulic conditions affect the mobilisation of discolouration material has yet to be thoroughly investigated. In this paper, results are presented from real turbidity and flow observations collected from three U.K. trunk main networks over a period of two years and 11 months. A methodology is presented that determines whether discolouration material has been mobilised by hydraulic forces and the origin of that material. The methodology found that the majority of turbidity observations over 1 Nephelometric Turbidity Units (NTU) could be linked to a preceding hydraulic force that exceeded an upstream pipe's hydraulically preconditioned state. The findings presented in this paper show the potential in proactively managing the hydraulic profile to reduce discolouration risk and improve customer service.

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“…For the simulations that follow, the demands were set at the expected average daily value multiplied by a peaking factor of 1.3 to represent the highest demand over the course of a day. Field work by Blokker et al () suggests that the threshold for self‐flushing pipes is between 0.10 and 0.25 m/s, and the lower threshold of 0.10 m/s is used here.…”

Section: Design Of the Researchmentioning

confidence: 99%