Managing Algal Blooms using Watershed Management and Treatment Plant Approaches

Canadian Water Network (2019)

Challenge

Harmful and nuisance algal blooms are a recurring issue for municipalities across Canada. Algae are naturally occurring phenomena in almost all aquatic environments, but the severity, frequency and geographical distribution of algal blooms are increasing globally. Some of the factors contributing to these increases are human activities such as agriculture and urban stormwater runoff that contribute nutrients like phosphorus and nitrogen, as well as increasing temperatures, changing precipitation patterns and changes in the freeze-thaw cycle due to climate change.

Algal blooms result in a number of impacts to society and the environment. Toxin-producing strains of algal blooms can impact human health, potentially causing illness or death if ingested directly through exposure during activities like swimming. In addition, algal blooms can impact drinking water treatment plant operations if they are present in source water. Potential impacts include clogged intake screens, impeded settling processes, taste and odour issues, and increased demand for coagulant and chlorine. Algal blooms may also cause negative ecological impacts in watersheds, including creating low-oxygen zones as they decay and shading aquatic plants, both of which impact the growth of aquatic fauna. Finally, algal blooms may result in economic and social impacts. They may impact the aesthetic value of beaches and coastal zones, which impacts the recreational use of these areas and tourism. They can also result in higher operational costs for municipal drinking water treatment plants and drinking water advisories can harm customer confidence.

The wide-ranging impacts of algal blooms are causing municipalities across Canada to consider potential solutions for their management and mitigation.

For more information, see the webinar backgrounder.

Project

In 2019, Canadian Water Network hosted a two-part webinar series on the strategic management of algal bloom impacts on local water sources.

The first webinar focused on reducing and minimizing algal blooms in drinking water sources using watershed management approaches. Three leading practitioners provided an overview of their experience with algal blooms impacts and how looking at the issue with the watershed characteristics in mind can result in effective and holistic management approaches.

Webinar 1 recording: Managing Algal Blooms in Drinking Water using Watershed-Scale Approaches 

The second webinar considered how the impacts of algal blooms can be managed in drinking water treatment plants. Three leading practitioners discussed the impacts they have observed in treatment plants and how they have worked to mitigate these impacts either through the implementation of advanced treatment technologies or through the optimization of treatment plant processes.

Webinar 2 recording: Managing the Impacts of Algal Blooms in Drinking Water Treatment Plants.

Outcomes

Addressing the impacts of algal blooms requires a holistic management approach due to the complex interaction of factors which determine whether algal blooms will occur, as well as their severity and frequency. In many cases, algal blooms cannot be completely prevented or eliminated, so management approaches should strive to improve the prediction of algal blooms through monitoring approaches and limit negative impacts through active mitigation, such as promoting agricultural BMPs and optimizing drinking water treatment plant operations to better respond to algal blooms when they do occur.

This two-part webinar series also highlighted that the scale at which management approaches are implemented must be considered. Both treatment plant scale and sub-watershed/watershed scale approaches may be effective, but typically require coordination among different stakeholders and decision-makers. Ultimately, there is no one-size-fits-all solution for the management of algal bloom impacts. Successful mitigation approaches require consideration of how climate change is impacting a municipality at a local scale, human activities within the municipality which may be contributing to algal bloom proliferation and the overall history of activities within the municipality which may be creating legacy issues that are now contributing to algal blooms.