WC146 JanFeb 2026 - Magazine - Page 35
Toronto’s Ashbridges Bay Treatment Plant uses a biosolids
pelletization program to turn sewage sludge into fertilizer pellets,
reducing waste, odor, and transport costs. Toronto and Region
Conservation Authority
Toronto and Region Conservation Authority
What makes pelletization different from other biosolids management methods such as land application or
incineration?
MICHAEL VUJICIC (VEOLIA): You don’t really find a lot of
pelletizers out there, and because of that, the knowledge base around operating them well, operating them
safely, operating them for long periods, really doesn’t
exist. It’s not well documented. The only people that
know pelletizers are the people who learned them
through experience. Every facility treats water upstream
in different ways, which affects the nature of the sludge
you’re producing. Even though you’re using a similar
technology from one city or municipality to the other,
because of your upstream processes, you really are
changing the dynamics of the sludge.
The lack of real industrial knowledge around the
process, combined with the fact that it’s very site
specific, really makes operating these types of facilities
challenging.
Toronto has been pelletizing biosolids at Ashbridges
Bay for over 20 years. Why did the city pursue this
pathway, and how has the program evolved?
PETER MARTO (CITY OF TORONTO): At one point, Ashbridges Bay used to incinerate all its biosolids. In 1998
the environmental assessment was conducted, and it
was agreed that incineration was no longer acceptable
for our facility and the City of Toronto. We produce
approximately 150,000 dry tonnes of biosolids per
year. One of the hardest parts for us was convincing
the public and farmers to get over the stigma of using
a human waste product as fertilizer. But we succeeded.
Biosolids have now gone from a waste product to a
commodity where farmers and others use it, see the
results and see the savings.
WAT E R C A N A D A . N E T
From an agricultural and environmental science
perspective, how do pelletized biosolids compare to
conventional fertilizers?
RYAN PROSSER (UNIVERSITY OF GUELPH): One of the big
things biosolids bring that synthetic fertilizers don’t is
organic matter. They not only provide nutrients that
plants need for growth, but they improve soil health
and soil quality.
VUJICIC: Soil is a living, breathing organism. Having
macro- and micronutrients along with organic matter
really makes these soils long-term sustainable. Synthetic fertilizers only return a specific nutrient like nitrogen
or phosphorus—they don’t add to long-term health.
People that are using this product can revitalize soils
that had deteriorated.
WATER C AN ADA • JANUARY/ FEBRUARY 2026
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