Moving Material: Hydraulic Management of Drinking Water Quality

It is recognised that material accumulates in Drinking Water Distribution Systems (DWDS) as a result of cohesive layer and sedimentation processes and when mobilised can lead to water quality issues such as discolouration. Whilst both accumulation processes are hydraulically driven, the hydraulic conditions leading to sedimentation are not understood, and yet this is considered a key cause of discolouration customer contacts and service dissatisfaction. This research aimed to improve understanding of material behaviour processes in DWDS and in particular identify where sedimentation may dominate, resulting in localised discolouration risk. This type of accumulation has been defined in this work as Localised Elevated Material Accumulation (LEMA).
The novel approach of considering both sedimentation and cohesive layer processes was adopted throughout the research's three-pillared approach, consisting of laboratory experiments, field experiments, and hydraulic modelling. Laboratory experiments analysed turbidity patterns to evidence the interactions between hydraulic conditions and discolouration material behaviour and found accumulation is best described using Reynolds number and mobilisation by shear stress. Using long-term repeated field work experiments, pipe-specific turbidity responses were mapped, and a novel approach was developed to differentiate the contribution of cohesive layers and sedimentation processes, allowing for the first time LEMA pipes to be identified. All-connection hydraulic models at 36 second temporal resolution were shown effective in determining the hydraulic metrics required to describe discolouration risk. The findings from each research pillar were integrated and refined into a framework that identified the best combination of Hydraulic Discolouration Metrics (HDMs) to capture LEMA. This LEMA framework can now be used by water companies to identify where sedimentation dominates, allowing targeting of resource efficient and effective maintenance to improve service and reduce discolouration customer contacts.