210687 Pathogen Risks Associated with Distribution Systems

Monday, November 9, 2009: 8:50 AM

Nicholas J. Ashbolt, PhD , Office of Research and Development/National Exposure Research Laboratory, US Environmental Protection Agency, Cincinnati, OH
     
Waterborne outbreak investigations associated with drinking waters identify two key issues. Firstly, looking at complete water supply systems (from watersheds, through water treatment to distribution), failure of distribution systems are the major single component responsible for the majority of drinking waters outbreaks in the US. Secondly, Legionella pneumophila is the most commonly identified agent responsible for these outbreaks. Hence, aging infrastructure and operational issues appear to lead towards fecal pathogen intrusions and contamination of drinking water (via cross-connections, backflows, mains repairs & sudden pressure changes etc.). On the other hand, pneumonia from Legionella and other opportunistic bacterial pathogens represent growth of indigenous microbes within distribution/in-premise plumbing systems, unrelated to fecal contamination. Therefore maintaining a residual disinfectant within distribution systems is considered appropriate to aid in the control of fecal intrusion pathogens and to reduce the growth of indigenous pathogens; noting that most disinfection byproducts (chemical reaction products produced from reactions between natural organic matter and the disinfectant, such as chlorine) are produced during primary disinfection at water treatment plant, some of which are potential carcinogens. In summary then, we monitor for fecal pollution to drinking waters via testing for viable E. coli. In the future, we may move more towards quantitative polymerase chain reaction (qPCR) assays, possible with chemical pretreatment to aid in resolving between dead and viable cells, and target a broader range of fecal-associated microorganisms. For the opportunistic pathogens, pre-enrichment for intracellular pathogens (in amoeba co-culture) and qPCR are approaches under evaluation.

Learning Objectives:
Describe how pathogens can enter drinking water distribution systems through intrusions, cross connections, and back-flow.

Keywords: Water Quality, Water

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: Dr Nicholas J. Ashbolt is a Title 42 Senior Research Microbiologist with the National Exposure Research Laboratory, U.S. EPA Cincinnati (since January 2007). Previously he was Head of the School of Civil and Environmental Engineering at the University of New South Wales (UNSW) Sydney. He has 25 years of experience in environmental microbiology, with a focus on the fate and transport of environmental pathogens. Over the last 10 years he has worked in joint Australian-Sweden and European programs developing methods to interpret pathogen data with the aid of quantitative microbial risk assessment within an urban water sustainability framework. This work has contributed to the risk-based approach adopted in the recently published WHO recreational, drinking and reuse water guidelines. He has published 27 book chapters, 110 journal papers and over 100 conference proceedings since he joined UNSW in 1994. His research at EPA is focused on distribution system pathogen risks and application of QMRA to drinking and recreational waters.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.

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