Cover of Microbes in Pipes: The Microbiology of the Water Distribution System

Non-microbiologists may assume that the goal of water utilities should be the elimination of all microbes from our drinking water. But the water we drink has never been sterile; perfectly safe water contains millions of non-pathogenic microbes in every glassful. Like every other human-built environment, the entire water distribution system — every reservoir, every well, every pipe and every faucet — is home to hundreds or thousands of species of bacteria, algae, invertebrates and viruses, most of which are completely harmless to humans. In April, 2012, the American Academy of Microbiology convened a colloquium to assess what is known about the microbial inhabitants of the water distribution system and to propose goals for advancing our understanding of these communities in order to enhance the safety of our drinking water and the resilience of our water infrastructure.

Most microbes in distribution systems probably do not pose health threats, but when they form biofilms, they can cause physical damage such as corroding pipes and blocking valves. In addition to forming biofilms, some non-pathogenic microorganisms can break down chemicals used to minimize microbial growth and others may release nutrients into the distribution system that support downstream growth of opportunistic pathogens. The extent to which these processes occur in water distribution systems is largely unknown, because these ecosystems have not been characterized. "The microbes that live in the water distribution system have many important effects," says Norman Pace, University of Colorado, Boulder. "We need to be able to tell the difference between a healthy, stable microbial community and one that threatens public health or infrastructure resilience."

The tools and expertise needed to characterize complex microbial communities are rapidly advancing and water distribution systems could prove to be excellent model environments. "Collaboration between water utilities and academic microbial ecologists could have benefits for both groups," says Michael J. Beach of the Centers for Disease Control and Prevention. "What we learn could enhance the safety and resilience of the distribution system while advancing fundamental understanding of microbial communities at the same time." An American Academy of Microbiology colloquium in April, 2012 brought microbiologists together with experts from many other science and engineering communities to identify specific challenges and gaps in our understanding of the microbial ecosystems of water distribution systems, and develop a research plan to address them. The colloquium’s discussions and the participants’ proposed research plan are presented in the report "Microbes in Pipes: The Microbiology of the Water Distribution System."

The colloquium was sponsored by the Alfred P. Sloan Foundation, which is funding a new field of scientific inquiry – the microbiology of the built environment. "The report explains many important concepts in very simple terms and will be useful in the foundation’s efforts to study these complex ecosystems," says Paula Olsiewski, program director Alfred P. Sloan Foundation. "While it is difficult to predict what will be discovered on the frontier of scientific inquiry, the opportunity exists to influence construction practices and other industrial processes to impact human health and well-being."


Michael Ingerson-Mahar, Ann Reid. 2013. Microbes in pipes: the microbiology of the water distribution system.

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