WC141 MarApr 2025 - Magazine - Page 18
TOP 50 PROJECT
Underground electrical infrastructure on Lot 2.
technical wizardry—its landscaping. But Lots 8 and 9 are both
associated with the production and handling of oxygen, a key
ingredient in producing ozone. Specifically, Lot 8 covers the purchase of oxygen generating equipment, while Lot 9 encompasses
the design and construction of buildings to house equipment
such as a vacuum pressure swing absorption (VPSA) unit designed to extract oxygen from air.
When the project is completed and the plant becomes fully operational, the plan is to generate ozone, use a slipstream of effluent
water to carry the ozone into the wells where they will mix, and
release the finely dispersed gas that emerges in the form of bubbles
roughly three millimetres in diameter. “That’s determined to be
the most efficient bubble size for disinfection,” Paoloni explained.
“When that’s injected into the stream, it’s like an inverted donut
where the gas and water go up from the bottom and then climb
upwards through the well, and as it’s doing that it disinfects [and
destroys] the bad material in our wastewater.”
While ozonation is considered highly effective, its deployment is a careful balancing act. The ozone that will be produced
on-site is highly corrosive. This attribute is key to disinfecting
germs and destroying synthetic pollutants, but ozone’s ability to
corrode also presents a challenge. “You have to generate it and
then use it as soon as possible because, the more time goes by,
the more it degrades back to fundamental oxygen molecules,”
Paoloni said.
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WATER C AN ADA • M ARCH/APRIL 2025
The ozonation project, aimed at reducing
pollution in the St. Lawrence, has dovetailed
neatly with another environmentally minded
project announced more recently for the JeanR.-Marcotte plant—converting four multiple-hearth incinerators into a combination of
biodigestors and fluidized bed incinerators.
The plant currently generates 275,000 wet tons of dehydrated sludge annually, and the four burners reduce this to
47,000 tons of wet ash (dry ash conditioned with water). This
ash, once transported to landfill, is used as fertilizer on nearby
farms. But the incinerators, built in 1988 and reaching the end
of their projected lifespan, have become costly to maintain and
are releasing nearly one-third of the greenhouse gases emitted
by City-owned operations. The incineration conversion project
represents an opportunity to review the way in which sludge is
treated and the process used for recovering residual materials,
the City said in a separate statement that promised the twin
benefits of producing clean energy and drastically reducing
carbon emissions.
The biodigestors and fluidized bed incinerators are complementary. The biodigestors will process 40 per cent of the
sludge by thickening it, subjecting it to anaerobic digestion,
dewatering and thermal drying, all to produce and recover biogas and pellets (dry digestate). The remaining 60 per cent of
the sludge will be dewatered and undergo fluidized bed incineration with thermal energy recovery, a process where sludge,
mixed with sand, is burned at temperatures high enough to
produce energy that can be used to heat the biodigestor system
and the Jean-R.-Marcotte buildings.
The conversion project’s feasibility study was completed
earlier this year, design work is underway, and work is slated to
begin in 2028, with commissioning anticipated by 2033.
The ozonation and incinerator conversion projects are part
and parcel of Montréal’s 2030 Strategic Plan, which emphasizes sustainable development, biodiversity and green spaces, and
management of the city’s riverside and aquatic natural heritage.
As mayor of the borough of Lachine, Maja Vodanović has
served on Montréal’s executive committee for waterworks and
is excited about the ozonation project because the plant treats
45 per cent of all the sewage in Québec and also handles rainwater. “The current goes upstream, so this will benefit all the
cities north of Montréal as well as the fauna and flora of the St.
Lawrence River,” Vodanović said.
Vodanović offered similar praise for the incinerator conversion project’s expectations to help Montréal significantly
reduce its greenhouse gas emissions. “It’s like getting 24,000
cars off the streets,” she said.
WAT E R C A N A D A . N E T
Ville de Montréal
“The ozone that will be produced on-site is highly corrosive.
This attribute is key to disinfecting germs and destroying
synthetic pollutants…”
