Climate event driven impacts to drinking water treatment in Atlantic Canada
Ryan Swinamer (Dalhousie University)

We have previously demonstrated that surface drinking water facilities in Atlantic Canada experienced 2 to 4-fold increases in natural organic matter concentration measured as color and dissolved organic carbon DOC over two decades 1999-2022 due to indirect climate impacts such as more stringent regulations and controls on air pollution and a shift away from coal for electricity. Analysis of historical operational data at Atlantic Canadian drinking water facilities revealed that the coagulant demand also increased at a similar rate. In summer 2023, extreme climate events e.g., drought, wildfires, and floods in Atlantic Canada, highlighted the necessity to assess the additional impact of climate events on raw water quality and drinking water treatment practices.

This presentation will provide an updated analysis spanning over two decades 1999-2023 of climate, water quality, and operational data from two drinking water facilities in Atlantic Canada. The overall goal was to assess the impact of extreme weather events on acute NOM concentration increases and drinking water treatment processes. In 2023, a dry spring combined with a warm and wet summer presented unique conditions that caused NOM in the water supplies to increase by at least 67% as measured by lake color. To mitigate increased NOM concentration, alum dose nearly doubled in 2023 compared to 2022. Regardless, disinfection by-product DBP formation in both distribution systems were elevated following the event but remained within compliance levels. Meanwhile, from 1999-2023 the two plants responded to long term climate change impacts with an increase in alum dose of between 3.5 to 9.7 times. Equivalent CO2 emissions were estimated for the production and transportation of alum, which increased by 3 to 7-fold in 2023 compared to when the plants were commissioned decades prior. It is therefore important to assess and plan for both climate adaptation as well as mitigation aspects for drinking water treatment design and resiliency as we continue to feel the effects of climate change in Atlantic Canada and beyond. An approach that considers both what treatment is required for future water quality paired with options analysis that includes the overall carbon cost of different alternatives will ensure that we can become climate resilient.