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Tonnes of treated sewage to be buried in landfill

By: Bartley Kives

Posted: 04/23/2011 1:00 AM | Comments: 0

The City of Winnipeg will bury approximately 13,000 tonnes of treated sewage in the Brady Road Landfill this year to comply with provincial regulations that forced the city to stop spreading the sludge over croplands.

But this disposal method is temporary, as Winnipeg's water and waste department is preparing to build a new biosolids plant that will allow the city to convert treated sewage into compost, electricity or an environmentally acceptable form of agricultural fertilizer.

Up until this year, the City of Winnipeg disposed of biosolids -- the waste-management industry term for the semi-solid substance commonly known as treated sewage sludge -- by spreading the material over farmers' fields. Farmers were not charged for the fertilizer-rich material, which is comprised of both waste and the remains of the beneficial bacteria used to digest it as part of the sewage-treatment process.

The practice of spreading biosolids on croplands ended on Jan. 1, due to nutrient-management regulations developed to reduce the amount fertilizer flowing into Lake Winnipeg, where excessive amounts of nutrients are causing algae blooms and disrupting the lake's ecology.

Now, biosolids are shipped by truck from a plant at Winnipeg's North End Water Pollution Control Centre to Brady Road, where the treated sludge is blended in with garbage and buried, said Nick Szoke, a senior engineer with the city's water and waste department.

This practice will continue until the water and waste department and consultants from Veolia Canada develop plans for a new biosolids plant that will replace the existing North End facility, at a cost of $150 million.

The construction of this plant is slated to begin in 2013, city budget documents show.

The plant will be designed in concert with a new primary sewage-treatment plant at the North End site currently slated to cost $365 million, said water and waste director Barry MacBride.

That price tag may decline if the province backs off from its insistence the city remove dissolved nitrogen as well as phosphorus -- the chief culprit in the decline of Lake Winnipeg -- from liquid sewage. A dispute over the environmental science behind nutrient removal is one of the chief sources of tension between Mayor Sam Katz and the Selinger government.

Regardless of which side wins this dispute, the new biosolids plant will allow the city to find a use for its treated sludge.

New equipment could be purchased that would allow the city to resume spreading biosolids over farmland, albeit over a much wider area, Szoke said. "The existing method doesn't allow us to spread it as thinly as the new regulations require," he said.

As well, the city could take residual phosphorus from the liquid-sewage stream and donate or sell the fertilizer to farmers.

"We can look at it as a revenue-generating source or as a revenue supplement for farmers," Szoke said. "If we're recovering phosphorus and there's a huge market for phosphorus, it could be a source of revenue for the city."

The city could also convert biosolids into compost, which could also be sold or donated. Alternately, the treated sludge could be converted into pellets that could be burned in furnaces to generate electricity. Veolia Canada already does this with biosolids in Toronto. "It really is a fuel source. And when you oxidize it at high temperatures, you don't get any of the byproducts you get at lower temperatures," Szoke said.

All of the city's waste-management plans, however, are subject to environmental approval from the province, which ordered the city to embark on A 30-year program of sewage-treatment upgrades back in 2003.

Together, the biosolids plant and the primary treatment plants at the North End and South End Water Pollution Control Centres will cost $751 million alone. The entire upgrade is expected to cost at least $1.8 billion by 2030 and possibly billions more, as the city has yet to decide how to replace its combined sewers.

bartley.kives@freepress.mb.ca

Republished from the Winnipeg Free Press print edition April 23, 2011 B2

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