The role of trunk mains in discolouration

Abstract

Understanding and managing the causes of drinking water discolouration are key challenges for the worldwide water industry. Discolouration is a major cause of customer contacts, undermining consumer confidence. Despite significant investment in the UK in the last 15 years in replacing/lining cast iron pipes and improving water treatment processes, discolouration continues to be an issue. Evidence is presented suggesting that trunk mains, which have largely been ignored in terms of rehabilitation and maintenance strategies for controlling discolouration, play an important role in discolouration. Three main datasets are presented to evidence this: discolourationrelated customer contact data, analysed utilising a novel cluster procedure; results from distribution network flushing studies pre-and post-cleaning of the supplying trunk main; and associated long-term trunk main turbidity and flow data. It is shown that a significant proportion of discolouration events affect multiple areas simultaneously, that trunk mains can act as a store of material, which can migrate downstream seeding the distribution systems and that the presence of material layers on the trunk main pipe surfaces demonstrates an inherent discolouration risk. Overall the results suggest that if discolouration is to be addressed, then any effective strategy must include the risk presented by trunk mains.

Water quality event detection and customer complaint clustering analysis in distribution systems

“…When clustering the contacts temporally, it was opted to do this as one group across the three DMAs. The DMAs were interconnected and served by one water source and studies have shown that over 40% of CCs are explained by clusters affecting multiple DMAs (Husband et al, 2010). The total individual customer contacts in the three DMAs for the one year period was 223.…”

Ensemble Decision Tree Models Using RUSBoost for Estimating Risk of Iron Failure in Drinking Water Distribution Systems

“…& Water quality sampling data linked to DMA & Water chemistry data for Service Reservoirs (SRVs) and Water Treatment Works (WTW) & Water supply system connectivity such as which WTWs supply which WQZ (and hence DMA) and which SRVs supply which DMAs & DMA information: % of certain types of pipe material calculated from overall pipe lengths & Clusters of customer contacts: individual customer contacts are rarely indicative of a widescale water quality problem, but multiple contacts within a short time window could be (Husband et al 2010). The Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm was used in MATLAB to identify temporal clusters of contacts (Ester et al 1996).…”

Data-Driven Study of Discolouration Material Mobilisation in Trunk Mains

“…While the hydraulic mobilisation of iron and manganese deposits has been long known to result in discoloured water, the presence of discoloured water can also be due to other processes such as biofilm mobilisation or chemical interactions between pipe materials and water acidity [7][8][9][10][11]. Discolouration has been shown to significantly vary even between different parts of the same water distribution network and yet is still similarly experienced throughout different countries regardless of widely-varying factors between their Water Distribution Systems (WDS) [12][13][14].…”

“…Once a sufficient number of discolouration complaints have been reported in the area, the company may decide to reline (or replace) old mains believed to be the cause of significant discolouration [6,11], particularly if this is going to help address additional issues (e.g., leakage). However, cleaning and especially rehabilitating WDS mains is expensive and can still potentially only have limited effect if the discolouration material was mobilised from a different section of the network [15].…”