Rising ammonia concentrations in Saskatoon’s wastewater system and the prospect of stricter provincial regulations are prompting the city to introduce tougher controls on industrial discharges.
According to a report presented to the city’s Standing Committee on the Environment, ammonia concentrations at Saskatoon’s wastewater treatment plant (WWTP) influent have increased by more than 65% over the past decade, driving up treatment costs and creating new compliance challenges.
Mike Sadowski, manager of Saskatoon’s wastewater treatment plant, told a recent public meeting that it cost the city approximately $726,000 in 2024 to remove total Kjeldahl nitrogen (TKN), a standard industry measure of nitrogen in wastewater that includes ammonia and other compounds that can convert to ammonia.
The move comes as the provincial Water Security Agency (WSA) prepares to introduce more stringent ammonia discharge limits aimed at protecting the South Saskatchewan River and surrounding aquatic ecosystems.
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Current limits in the plant’s Permit to Operate allow ammonia concentrations of 17 milligrams per litre from October 1 to June 30 and six milligrams per litre from July 1 to September 30. City administration expects future requirements to impose a year-round limit below six milligrams per litre.
While the Saskatoon WWTP currently meets its regulatory permit requirements, the committee report notes that the city has adopted stricter environmental performance targets intended to better protect aquatic life. Ammonia concentrations can occasionally exceed those internal targets during winter months when colder temperatures reduce the activity of the bacteria responsible for removing ammonia during treatment.
Excess nitrogen in waterways can contribute to algal blooms, which block sunlight, reduce oxygen levels as they decompose, and can harm fish populations and aquatic ecosystems.
To address increasing treatment costs and prepare for future regulatory requirements, Saskatoon plans to reduce the allowable ammonia concentration in industrial wastewater discharges from 100 milligrams per litre to 50 milligrams per litre. The city also intends to introduce a surcharge for companies that exceed the new threshold.
The proposed changes, expected to take effect in 2028, are designed to encourage industries to either invest in on-site treatment systems or contribute financially to the city’s costs of removing excess ammonia before treated effluent is discharged to the river.
Currently, those treatment costs are borne by all wastewater ratepayers.
The committee report notes that Saskatoon’s approach aligns with practices adopted elsewhere in Canada. A review of sewer use bylaws in 13 major Canadian municipalities found that all currently regulate TKN concentrations in industrial discharges. Eight municipalities already apply surcharges for exceedances, while three others are preparing to implement similar fee structures.
City officials say the changes will help ensure that industrial users contribute more directly to the costs associated with treating high-strength wastewater while supporting compliance with anticipated future environmental regulations.
