In case you missed it: Top 4 things you should know about discharging effluent in a changing climate

As our climate changes, we’re seeing fluctuations in weather patterns across Western Canada. Drought conditions and rising temperatures are causing low water flows in rivers, or modifying the timing of high and low flow periods. What does this mean for the industries who release wastewater (effluent) into rivers? How can these businesses prepare for a future where the amount of effluent they’re allowed to discharge into water bodies might be reduced?

Robert Best, Senior Aquatic Ecologist, answered these questions and more in his presentation ‘Discharging of Industrial and Municipal Effluent in a Changing Climate’ at EnviroTech 2022. In case you missed it, here are the top 4 things you need to know:

1. Water users fall into three broad categories: Communities, Businesses, and the Environment. They all use water, and they all discharge wastewater (also called effluent). Communities use water for drinking, general household use and recreation, and they discharge sanitary sewage as treated effluent. Businesses use water for drinking, irrigation and agriculture, manufacturing, mining, and hydroelectric generation, and they discharge sanitary sewage and industrial waste as treated effluent. The environment uses water for the natural cycle of rivers, creeks, lakes, and wetlands and discharges greater volumes of water during the freshet (the spring thaw from snow and ice melt in rivers).
2. Past weather patterns can give us insight into future conditions. Between 2015 and 2021, British Columbia faced extreme drought, resulting in low water flow in some rivers. ‘Low flow’ can be determined by the critical environmental flow threshold, which is ‘a short-term flow threshold, below which, significant or irreversible harm to the stream's aquatic ecosystem is likely to occur.’ With these low flows, drought conditions can worsen naturally occurring events like wildfires and floods. Drought contributed to the devastating wildfire in Fort McMurray, AB in 2016 and in Lytton, BC in 2021. Two atmospheric rivers followed the wildfires in 2021, and the combined effects of the burned land and heavy rain caused catastrophic flooding and landslides. It’s predicted that the changing climate may extend periods of low flow in rivers and make significant weather events more intense.
3. Low river flows can have potential impacts on water users. Recently, in the Coldwater River Basin, BC, the lowest recorded flow was 10 times lower than the threshold. This extremely low flow may be stressing juvenile fish and can impact the survival rates and spawning activities of resident and migratory fish species, and other aquatic life. For communities who rely on water from the Coldwater River, when a water shortage is declared their water rights can be restricted and suspended for uses beyond essential household needs. Recreational water users and businesses who rely on fisheries can also be affected by angling restrictions imposed due to increasing water temperatures which may lead to higher mortality in fish.
4. Changes to conditions in aquatic environments may lead to reduced effluent discharge limits. We’re seeing changes in baseline conditions like water temperature, dissolved oxygen, nutrient levels, and natural flow. These conditions may lower the ability of a body of water to dilute wastewater. This means the ability of the aquatic receiving environment to adequately mix and dilute effluent may be reduced, creating potentially toxic conditions for wildlife. If the anticipated dilution ability of the water might not be met, discharge limits may need to be decreased, and discharge permits may be required to change. Industrial dischargers of wastewater could potentially exceed the provincial or federal water quality guidelines, and face non-compliance orders if they’re not careful.

Municipal and industrial operators should consider proactive planning to futureproof their approach. Operators should focus on understanding the aquatic receiving environment and consider more robust programs that can provide an early warning system for operations; they should try to reduce their reliance on discharging effluent from industrial processes into surface water bodies, by increasing their use of alternative sources of waste products and considering investment in water recycling technologies; and lastly, they should look into operational planning for discharging wastewater outside of sensitive time windows.

By incorporating these actions, businesses can become more resilient to climate change-induced shifts in water conditions. The overall goal is the sustainability of water resources for all users, now and in the future.

For more information about this presentation, contact Robert Best or visit our Ecology service page.