Jonathan Clayton is a PhD student at the University of Alabama studying the effects of leaks and negative pressure events in water distribution systems.

Life Cycle Analysis of a Water Distribution System to Evaluate Aging Effects on Optimal Pipe Replacement Frequency

Co-authors: Jonathan Clayton, Ricardo Mejia, Daqian Jiang, and Leigh Terry

Drinking water distribution systems (WDS) are integral to the urban water cycle, public health, and urban infrastructure as they transport treated water, often over large distances, while maintaining the chemical and biological integrity of water throughout the network.

A key challenge in the operation of WDS is determining the pipe replacement frequency.  According to a 2012 study, operators in the U.S. and Canada replace pipes every 125 years on average due to the high costs of pipe manufacturing and installation. Meanwhile, the average age of failing water mains is 50 years according to the same study. As a result, much of the nation’s pipe is due for replacement in what the AWWA has referred to in their “Dawn of the Replacement Era” (2001) and “Buried No Longer” (2011) publications as the “Replacement Era” with high cost-estimates of maintenance and upkeep lasting until 2050. Neglecting to replace pipes at the appropriate time can potentially lead to significantly increased chemical/energy consumption and undesirable human health and environmental impacts as pipe leaks, tuberculation, and chlorine decay are functions of pipe age.

Past life cycle analysis studies on WDS have not accounted for the myriad effects of pipe aging. Thus, this study will incorporate pipe-aging factors into a cradle-to-grave life cycle analysis of a water distribution system in the southeastern United States.  This allows decision makers to interface with the wholistic costs of their decisions rather than only those with which they directly interface.

The analysis will be performed for five scenarios over which pipe replacement occurs every 25, 50, 75, 100, and 150 years. Hydraulic and water quality simulations in EPANET 2.2 will ensure regulatory standards are met. Additionally, leaks in the system will be simulated using a Weibull-Exponential-Exponential (WEE) statistical model. Finally, OpenLCA v1.11 software and the EcoInvent v3.7 and World Steel 2020 databases will tie each component of the system to its environmental and human health impacts. Impacts will be quantified for acidification, carcinogenic substances, non-carcinogenic substances, ecotoxicity, eutrophication, fossil fuel depletion, global warming, ozone depletion, respiratory effects, and smog.

The results will indicate an ideal pipe replacement frequency to advise operations staff how often they should replace the pipes in the system. Meanwhile, the components of the system that are most in need of attention will be highlighted so decision-makers can prioritize investments. These findings are important for developing preventative and corrective maintenance strategies to minimize the impacts of aging infrastructure.