Water quality in distribution systems: rehabilitation and maintenance strategies

This paper details work undertaken in a distribution system network area previously subject to rigorous rehabilitation works and pre and post assessment to confirm that improvements in water quality were made. Approximately 12 months after completion of these works, discolouration complaints were again received from a localized area of the network. Sections of the network were aggressively flushed in response to these complaints and the system response to these activities monitored. The isolated dead end pipe serving the area of customer complaints exhibited significant discolouration in response to the flushing. However, other pipes within the study area also exhibited discolouration response in excess of normal regulatory supply limits. The discolouration measurements obtained from this study were interpreted with respect to rates of material accumulation and discolouration risk based on the novel predictive discolouration modelling approach after Boxall et al (2001). The accumulation of material leading to discolouration, particularly in areas previously subject to comprehensive rehabilitation, has been shown to be a significant issue and the quantification of rates of accumulation and associated discolouration risk are essential for the development of distribution operation and maintenance strategies.