After Regina’s Wascana Creek was found to be one of the most polluted streams in Canada, the city spent $175 million on wastewater treatment plant upgrades that included biological nutrient removal, an endeavour that has so far cut levels of total dissolved nitrogen by as much as 85%.
Wascana Creek was described in a 2011 Environment Canada study as an “effluent-dominated ecosystem” battered by high levels of pollutants downstream from the EPCOR-operated WWTP. Five years later, Regina officials made some major improvements to the treatment plant.
The University of Regina has been tracking the creek’s recovery from eutrophication, caused by excess inputs of nutrients from the city, farms and industry. A situation that led to algae blooms, a collapse of biodiversity, and the activation of toxins from lake and river beds, has seen some rehabilitation, despite being exacerbated by climate change, which works with eutrophication to reduce oxygen in the water.
Wascana Creek flows northwest through Wascana Lake before receiving treated urban wastewater from the City of Regina and joining the Qu’Appelle River.
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Dr. Peter Leavitt, a University of Regina biologist and Canada Research Chair in Environmental Change and Society, worked alongside Nathanael Bergbusch, who led the study while working with Leavitt as a Masters student.
Leavitt said that while the removal of phosphorus from wastewater is known to reduce the production of blue-green algae in lakes and streams, “this is the first time that scientists have shown that nitrogen removal can also reduce freshwater eutrophication,” he noted in an announcement from the university.
High levels of phosphorus and trace levels of various pharmaceutical drugs were also revealed in the Environment Canada study, but the new biological nutrient removal (BNR) process has had little impact on the presence of phosphorus.
The University of Regina study took place over 10 years. Improvements continued over the length of the study, which looked at the three years before the wastewater system upgrades and the three years after.
While nitrogen removal has been somewhat controversial in wastewater circles, the study has shown some merit for communities considering BNR upgrades. The absence of evidence that selective nitrogen removal improves symptoms of eutrophication has fostered debate and contributed to limited adoption of BNR technologies by cities, the study states.
“These findings are particularly relevant to prairie and other Canadian communities currently debating the cost benefits of BNR wastewater treatment processes,” announced Bergbusch in a statement from the university.
