A Holistic Modelling Approach to Predict the Effects of Ageing Pipes on Water Quality in Distribution Systems

Prioritization of water mains for renewal requires the simultaneous consideration of their structural integrity and hydraulic performance as well as their contribution to the deterioration of water quality. Generally, the impact of deteriorating pipes on water quality in the distribution network has not been taken into account in the decision-making process. To address this issue, the National Research Council of Canada (NRC) and American Water Works Association Research Foundation (AwwaRF) embarked on a 4-year research project (FY 2003-2007) to investigate the effects of aging water mains on water quality in distribution networks. Numerous factors affect water quality in the distribution network and interactions amongst them are complex and often not well understood. Water quality failures in distribution networks are scarce, which make statistically significant generalizations difficult. However, the rarity of water quality failures belies their seriousness, since each failure indicates the potential for harmful public health effects and increased public mistrust and complaints. In such data-sparse circumstances, expert knowledge and judgment can serve as a supplemental or even an alternative source of information. At the NRC we have developed a soft computing-based model to predict water quality failures in distribution network. The model can incorporate uncertain, subjective/ linguistic and/ or incomplete data. The proposed model is based on an approach, called fuzzy cognitive map (FCM), which is a plausible way to represent and comprehend ill-defined and complex relationships that govern water quality in the distribution network. This paper provides a brief overview of the methodology and the approach developed in this research. Technical details have been published or submitted elsewhere in the refereed journals as well as international conferences.