Elucidating drinking water quality deterioration in premise plumbing

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Premise plumbing is the portion of the water distribution system associated with private or public buildings (e.g. homes, schools). Compared to the main distribution system, premise plumbing has unique features that make it more vulnerable to water quality deterioration, such as longer stagnation periods, higher surface area to volume ratios, and elevated temperatures. Premise plumbing water quality is also unmonitored by most regulatory regimes. Increased water age, a result of water conservation priorities and improved plumbing fixture efficiency, heightens the risk of water quality degradation due to chlorine decays and the resultant flourishing of surface attached microbial communities (biofilm). There is clear evidence that water-efficient buildings can support 10-10000 times more opportunistic pathogens relative to conventional buildings. Further, an estimated 8% of waterborne outbreaks (excluding Legionella) in the USA are associated with premise plumbing deficiencies, and the proportion of premise plumbing based outbreaks is increasing. Beyond the microbiological risk, premise plumbing has also been implied as a site for inorganic contaminant accumulation in both chemically or biofilm mediated deposits. Accumulated inorganics, such as arsenic (As) (carcinogen), lead (Pb) and manganese (Mn) (neurotoxins), represent a public health threat given that once accumulated on a surface, these toxins can be released into the water. Although premise plumbing is implied to have a significant role in governing inorganic water quality deterioration, it has not been the focus of controlled laboratory study. It is unclear how pipe materials, extended stagnation times, and water efficient configurations influence the accumulation and release of inorganic contaminants. This unique research program will identify, characterize, and explore the underlying biological and chemical mechanisms that govern the accumulation and release of inorganic contaminants (e.g. As, Pb, Mn) in premise plumbing. Ten HQP will train in an interdisciplinary environment and explore these mechanisms through three interrelated objectives that will examine i) the influence of pipe materials; ii) the role of stagnation/water age, including mimicking low flow conditions of water-efficient buildings; and, iii) the impact of upstream water quality and equilibrium shifts. This research program will grant fundamental mechanistic insights into the specific biological and chemical mechanisms (e.g. key functional groups for metal binding; metals surface deposit structure and characteristics) through which inorganics can accumulate and release. The new knowledge generated by this research will explain the underlying mechanisms and environmental conditions that govern inorganic contaminant accumulation/release in premise plumbing, newly equipping Regulators and Utilities in Canada, and globally, to make sound evidence-based decisions to minimize exposure risk and protect public health.