Infrastructure performance rating models for wastewater treatment plants

Wastewater treatment plants (WTPs) are among the most complex municipal infrastructure systems that serve large populations. Unfortunately, many studies have shown that the WTPs, in the USA and Canada, are facing unprecedented deterioration due to ageing and improper maintenance plans. This situation is aggravated by the lack of adequate funds for upgrading and maintenance. In 2008, Statistics Canada estimated that WTPs exceeded 63% of their useful lives, the highest level among public infrastructure facilities. Similarly, the WTP performance in the USA had a near-failure average grade of D − . These facts show the urgent need for rehabilitation decision tools to keep these facilities running effectively. This research aims to respond to such a pressing need by developing a condition-rating index (CRI) model for the WTP infrastructure. The CRI is developed using an integrated approach of the analytical hierarchy process with the multi-attribute utility theory. The required data for these models are collected via questionnaires from site visits and interviews with experts in Canada and the USA. The results reveal that physical factors have the highest impact on deterioration of WTP infrastructure and that pumps are the most vulnerable infrastructure unit. The developed CRI workability is proved using data of three WTPs from Canada and the USA, which show robust results.