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Great Slave Lake Nutrient Risk Assessment and Treatment Improvement Options Study Fiddlers Lagoon Wastewater Treatment


Yellowknife, NWT



Environmental Engineering

Water Treatment

Environmental Assessment

The City of Yellowknife currently treats municipal wastewater by a lagoon and natural wetland system known as the Fiddler’s Lake Treatment System.

The System operates under the requirements of a water licence issued by the Mackenzie Valley Land and Water Board. The wastewater undergoes treatment as it flows through a network of stream channels, ponds, and wetlands until it is discharged through an open channel to Great Slave Lake.

The City retained Associated to gain a better understanding of the risks presented by nutrient loading to Great Slave Lake to determine whether the current and projected future loading of nutrients poses a risk of causing eutrophication in the immediate receiving area of the lake. We also conducted an independent evaluation of the feasibility and effectiveness of the options for treatment improvement identified in the System Plan.

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Project Highlights

The 2017 monitoring program provided the first characterization of water quality in the receiving area of Great Slave Lake. To confirm the 2017 findings and assess year-to-year variation, we recommended monitoring the receiving area of the lake during the open water seasons in 2018 and 2019 for chloride, total and dissolved phosphorus, chlorophyll a, and other routine parameters. Our Treatment Improvements Options Analysis report provided possible treatment improvements and options for phosphorus removal.

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