Canadian Consulting Engineer

Winnipeg wastewater treatment plants stir emotions

Wastewater treatment processes don't often spark hot debate, but in Winnipeg they have been stirring emotions ...

October 5, 2009   Canadian Consulting Engineer

Wastewater treatment processes don’t often spark hot debate, but in Winnipeg they have been stirring emotions among city officials and hitting newspaper headlines.

At issue is whether the city should have to include advanced nitrogen removal in the upgrades it is undertaking for its wastewater treatment plants. The city is embarking on its largest capital project to date with upgrades to its North and South End plants, valued at around $600 million in total.

The province wants the city to include a process to convert nitrates into nitrogen gas so that the nitrogen will be released into the atmosphere as opposed to ending up in the Lake Winnipeg. The lake has been plagued with blue-green algae blooms, or cyanobacteria, and scientists don’t seem to agree on how to resolve the problem.

A report prepared by the Manitoba Clean Environment Commission and submitted to the provincial Minister of Conservation in March, recommended that to alleviate the algae problem, the City of Winnipeg should remove both nitrogen and phosphorus from its wastewater. That report was written by a panel based in part on earlier findings by Associated Engineering that looked into the cost of adding nitrogen removal. The panel also attended an expert symposium, and took into account recommendations from government agencies and the province’s Environment Act.

However, a group of 63 prominent scientists and engineers are questioning the wisdom of including nitrogen removal, saying that not only is the cost of removing nitrogen too high, but also that removing nitrogen could actually worsen Lake Winnipeg’s problem with blue green algae.

This group, which includes City of Winnipeg engineers, academics such as Professor D. Schindler from the University of Alberta, and scientists from Fisheries and Oceans Canada, prepared a poster for an environmental conference in Poland. Their poster, entitled “Environmentally Sensible Effluent Nitrogen Limits,” proposes “to show the disconnect between protecting the aquatic environment and the drive to reach increasingly lower nitrate nitrogen limits” in the Lake Winnipeg watershed. The group says that to implement nitrogen removal increases the carbon footprint of the plant, and “may in fact promote blooms of cyanobacteria in Lake Winnipeg.” They say the focus must be on removing phosphorus, not nitrogen.

This group calculates it will cost $430 million to overhaul the city’s North End plant to include nitrogen as well as phosphorus removal, whereas it will cost only $130 million to implement phosphorus removal only. Over 20 years, the added cost of nitrogen removal would be $750 more.

Discussing the issue in his annual report, the chair of the Manitoba Clean Environment Commission said, “Nutrient management has a significant impact on the health of Lake Winnipeg. The issue came fraught with baggage. Scientific opinion covered a very wide spectrum. Debate had become passionate, polarized, and public. It risked becoming overly simplified and too narrowly focused.

Several wastewater treatment plants in western Canada do remove nitrogen. However, Mike Shkolny, P.Eng., manager of water and wastewater for the City of Winnipeg, says that Winnipeg’s situation is very different to that of cities like Edmonton or Calgary which discharge into nearby rivers because Lake Winnipeg is 60 miles away from the city treatment plants.

Shkolny explains that the scientists who argue against removing nitrogen from the wastewater do so because they say that deprived of nitrogen in the water, the algae will actually simply compensate by capturing nitrogen from the air.

The Lake Winnipeg watershed is the second largest in Canada and serves 6.6 million people. The lake are itself is 24,500 square kilometres.

Shkolny says the city is proceeding according to the provincial guidelines and they are currently looking for “strategic partners” to help them design and build the upgrades to the North and South End plants.


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