Contaminant intrusion in water distribution networks: review and proposal of an integrated model for decision making

Contaminant intrusion in a distribution network (DN) refers to the entry of harmful chemicals and pathogens in the presence of three conditions: (i) the availability of a contaminant source near water mains; (ii) a pathway: leakage or breakage; and (iii) a driving force: low or negative pressure in the water main. The occurrence of contamination in a DN can take place frequently as there is no specific treatment at this stage except secondary disinfection. Contaminant intrusion requires as much attention as source water protection or treatment plants, particularly given that at this point, water is near the final stage prior to human consumption. Failure to detect and treat at this time could have potential negative impacts on consumers' health. Following the September 11, 2001 attack, strict regulations are now enforced by the municipalities to monitor water quality within DNs. This review article focuses on various aspects of contaminant intrusion in DNs based on more than 90 journal articles, peer-reviewed conference proceedings, and research reports. Here we present details on the conditions of contaminant intrusion, water quality regulations, sampling, protection and mitigation strategies, and various modelling approaches for decision making. Based on this review, we propose an integrated model that will help guide effective decision making for contaminant detection and mitigation.