The evidence is unequivocal – infrastructure in the United States is aging faster than it is being replaced . The deteriorating infrastructure includes water distribution systems, which provide the country with a constant supply of potable water. Water main breaks – particularly, the low-pressure events that are associated with them – have been associated with an increase in contamination in water systems and incidences of acute gastrointestinal disease [2-4]. This news is troubling, given that there are approximately 240,000 water main breaks in the US every year .
So how do these crises occur? Upon reaching the end of their useful life, the water distribution systems is more susceptible to losses of physical integrity, which leads to an increase in the number of breaks . In their 2006 report on risk assessment and reduction for distribution systems, the Committee on Public Water Supply Distribution Systems of the National Research Council defined a loss of physical integrity as when the system no longer acts as a barrier that prevents external contamination from deteriorating the internal drinking water supply . To contextualize the scope of the situation, it is important to note the current trends and state of water infrastructure in the United States. Due to a variance in construction styles, many pipes in the US are due for replacement in the upcoming years. In fact, the American Water Works Association estimates that the investments needed for buried drinking water total more than $1 trillion over the next 25 years . More than just a looming economic burden, there has been already been a marked increase in water main breaks in certain regions of the US . Clearly, aging water infrastructure in the US is a significant problem in economic terms – the rest of this report argues that the deterioration of our water systems also affects population health.
During 1971 to 2006, a total of 780 outbreaks associated with drinking water resulted in 577,094 cases of illness and 93 deaths . Although the annual number of reported drinking water outbreaks decreased considerably after 1980, outbreaks continued to occur, with an increasing proportion of them attributable to our distribution systems. Although ample evidence of an aging water distribution system in the US and the prevalence of WBDO via distribution systems exists, it is important to elaborate how these two phenomena are related. Water distribution is not a completely closed system; more than 10% of water is lost in many systems in the US, which may be attributable to breaks and leaks . To scale the amount of water lost in water distribution systems in the US, the United States Geological Survey (USGS) estimated that 1.7 trillion gallons of water are lost yearly in these systems . Part of the water loss is due to unpaid use, but much of the problem stems from the previously mentioned leaks and breaks, which are being exacerbated by the aging state of our nation’s infrastructure.
Central to the relationship between AWI and WBDO is that the deficiencies the physical integrity of the distribution system opens the possibility of microbiological contamination of the water from the external environment. If positive pressure is maintained, the possibility of contamination is low, but if a transient or low-pressure event occurs, the system is vulnerable to contamination [2-4]. Contamination via microbes surrounding distribution systems is a highly plausible scenario – Karim, Abbaszadegan, and Lechevallier found indicator microorganisms and enteric viruses in over 50% of their samples taken near water distribution systems . Related to the prevalence of deficiencies in the water distribution system, Tinker et al. have found that in Atlanta, GA, water that spends more time in the distribution system is more likely to cause an AGI .
Often, in the US, we take the potability of our water for granted, without thinking of the considerable distances the water must travel to reach our homes safely. It is of utmost importance that future policymakers acknowledge the gravity of the situation, and that the proper investments are made to mitigate the effects of aging water infrastructure. In the end, the problems delineated in this post offer a larger lesson in water sustainability -- constant maintenance, community awareness, and sound political decisions are key factors in the provision of safe drinking water. It is essential that we work towards providing this invaluable resource for not just the current population, but also for future generations as well.
1. Engineers, A.S.o.C., Failure to Act: The Economic Impact of Current Investment Trends in Water and Wastewater Treatment Infrastructure. 2011: Boston, MA.
2. Nygård, K., et al., Breaks and maintenance work in the water distribution systems and gastrointestinal illness: a cohort study. International Journal of Epidemiology, 2007. 36(4): p. 873-880.
3. Ercumen, A., J.S. Gruber, and J.M. Colford, Jr., Water distribution system deficiencies and gastrointestinal illness: a systematic review and meta-analysis. Environmental Health Perspectives, 2014. 122(7): p. 651-60.
4. Hunter, P.R., et al., Self-reported diarrhea in a control group: a strong association with reporting of low-pressure events in tap water. Clinical Infectious Diseases, 2005. 40(4): p. E32-4.
5. Agency, U.E.P., Addressing the challenge through innovation. 2007.
6. USEPA, Aging Infrastructure research Program: Addressing the Challenge through Innovation. 2007.
7. (Council), N.N.R., Drinking Water Distribution Systems: Assessing and Reducing Risks. 2006, The National Academies Press: Washington, D.C.
8. (AWWA), A.W.W.A., Buried No Longer: Confronting America's Water Infrastructure Challenge. 2011.
9. Craun, G.F., et al., Causes of outbreaks associated with drinking water in the United States from 1971 to 2006. Clinical Microbiology Reviews, 2010. 23(3): p. 507-28.
10. Kirmeyer, F., Martel, & Howie, Pathogen Intrusion Into the Distribution System. 2001, AWWA Research Foundation and the American Water Works Association: Bellevue, WA.
11. Karim, M.R., M. Abbaszadegan, and M. Lechevallier, Potential for pathogen intrusion during pressure transients. Journal / American Water Works Association, 2003. 95(5): p. 134-146.
12. Tinker, S.C., et al., Drinking water residence time in distribution networks and emergency department visits for gastrointestinal illness in Metro Atlanta, Georgia. Journal of Water & Health, 2009. 7(2): p. 332-43.
Fellow Alex Northrop