Evaluating microbial risks and performance criteria for safe management of stormwater and rainwater use in Alberta

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Alberta is faced with water quality and scarcity issues. Stormwater and rainwater are alternative water sources that can supplement growing water demands, but are plagued by: i) aging pipe infrastructure; ii) design challenges (i.e., combined sewer outfalls, illicit cross-connections); iii) the absence of North American pathogen-related criteria for safe reuse; iv) a lack of scientific data on pathogen/contaminant concentrations to estimate risks; and v) a lack of, or conflicting, regulatory policy framework in Alberta and Canada. These challenges have impeded the adoption of a province-wide regulatory framework. Since waterborne pathogens represent an acute risk, we propose to work with municipalities (Calgary and Airdrie) on evaluating the microbial risks associated with stormwater and rainwater reuse. Water samples from stormwater and rainwater systems will be collected and analyzed for microbial pathogens (viruses, bacteria, protozoans, helminths) and routine microbial water quality targets (E. coli, coliforms). Microbial source tracking will be done to identify sources of pollution impacting these systems. This data, along with other physicochemical parameters (precipitation, drainage flow, land-use, etc.), will be used to model pathogen transport in stormwater systems for evaluating microbial loading. The data will be fed into quantitative microbial risk assessment (QMRA) frameworks to evaluate water safety in terms of 'water-fit-for-purpose' under a variety of reuse scenarios (e.g., irrigation, toilet flushing, etc.), and the level of treatment determined for meeting risk targets. The information will also be used to develop water safety plans to manage pathogen risks. The project will be instrumental in developing and supporting sustainable water reuse in Canada by fundamentally grounding science-based evidence in regulatory development. In addition to decreasing dependency on potable supplies and reducing costs associated with infrastructure expansion, the benefits to Canadian society include drought control, long-term water supply management, lowering the ecological footprints of cities, and providing sustainable practices to support urban challenges in Canada's municipalities.