The province's environmental watchdog will decide in the next several weeks whether to radically rethink the cleanup of Lake Winnipeg, a move that could save taxpayers millions and clean up beaches faster.

Or not, depending on whose science you buy.

The Clean Environment Commission has spent the better part of the last five months hearing from the city's sewage system engineers, the province's water experts, scientists and environmentalists on whether to remove both nitrogen and phosphorus from Lake Winnipeg's watershed or just tackle phosphorus.

CEC chair Terry Sargeant says his report could be submitted to the Minister of Conservation in a matter of weeks, possibly before the end of the month and certainly before the end of April. It's a report that's hotly anticipated by city hall, which is in the midst of a $1.8-billion upgrade to its three sewage treatment plants and its pipes, but the CEC's recommendations could be felt by farmers, small municipalities and other nearby provinces and states.

"We've taken a broad look at the issue," said Sargeant. "We've looked beyond the city of Winnipeg's sewage treatment."

If the CEC comes down on the side of a phosphorus-first approach, that could save Winnipeg homeowners between $10 and $50 million, money that was slated to be spent on new technology to remove nitrogen from the treated waste water the city pumps into the Red River. The city, bolstered by some of Canada's best water scientists, has said removing nitrogen is a waste of money and could actually make Lake Winnipeg dirtier.

But the province has argued that ignoring nitrogen and the damage it does to the lake's ecological balance would be a half-measure.

After months of growing pressure from the environmental and scientific communites, the province asked the CEC last fall to wade through the mountain of evidence and opinion and rule on the N vs. P debate. The Doer government is expected to heed the CEC's recommendations, but both the city and province refused to comment on their submissions or what effect the CEC's findings may have on the volume of regulations and engineering plans both governments have already developed.

Sargeant said one thing the CEC's report won't do is lay out a new nutrient reduction target, even though critics, including Liberal Leader Jon Gerrard, have said the province's current one is too tepid.

Some of the country's top water scientists, including University of Alberta Prof. David Schindler, have said the province must cut phosphorus by 25 per cent in order for the lake to improve, and that means lobbying for the cleanup of the Red River south of the border.

The province has pledged to cut phosphorus by 10 per cent and nitrogen by 13 per cent.

maryagnes.welch@freepress.mb.ca

The N. vs. P dbate

What's the problem?

EUTROPHICATION, which means too many nutrients like nitrogen and phosporus are building up in the lake. These occur naturally or come from agricultural lands or human waste. Stinky blooms of blue-green algae thrive on nutrients, and can blanket the lake in summer. And they suck the oxygen out of the lake, killing fish and other aquatic life. The problem has gotten worse since the mid-1990s.

The case for phosphorus

The worst algae, the toxic blue-greens, can get nitrogen straight from the air. So the best way to starve them is to focus on removing the other nutrient they need, which is phosphorus.

'There are hundreds of lakes in North America and Europe where controlling phosphorus alone has successfully reduced eutrophication, including in lakes Erie and Ontario. There are no cases where controlling nitrogen has decreased eutrophication'

-- University of Alberta Prof. David Schindler, founder of the experimental Lakes Project near Kenora and one of the country's top experts on eutrophication

The case for nitrogen

Thirteen cities in Western Canada remove nitrogen from their waste-water stream and Winnipeg ought to do the same, especially since nitrogen loading in Lake Winnipeg is growing faster than phosphorus. Blue-green algae depend on nitrogen and phosphorus at different times in their life cycle, and it makes sense to go whole-hog, cleaning up all nutrients, instead of waiting another generation to see if a P-first approach works.

'In the last 30 years, we've added both nitrogen and phosphorus to the lake, and now we have to undo that. We cannot take half measures'

-- Dwight Williamson, acting assistant deputy minister of Water Stewardship