Rouyn-Noranda’s wastewater contains so many heavy metals that the sludge from wastewater treatment infrastructures in the urban part of the city cannot be recycled. A rare situation in Quebec that forces the city to bury her, possibly hundreds of kilometers away, at great expense.
Published at 12:43 am. Updated at 05:00.
Cadmium and copper, metals emitted in large quantities by the Horne Foundry, are found there in quantities exceeding the limits permitted for use as fertilizers, as is arsenic, to a lesser extent, according to a report by Viridis Environment dated July 2021, La Presse obtained.
The company, which specializes in the management of fertilizer residues, attributes the occurrence of these metals “to the regional background noise of the soil and to anthropogenic activities [c’est-à-dire d’origine humaine]around the city.
Regional soil background
Presence of pollutants in a given environment independent of human activity.
Viridis Environment was commissioned by the city to identify “potential solutions to enhance municipal biosolids” – which are rich in organic matter, nitrogen, phosphorus and trace elements such as iron, magnesium and manganese.
“Investigating the file does not allow us to find restorative solutions [permises] », but the company closes. The document lists options, all of which would require special approval from Quebec’s environment minister.
Agricultural application, typically permitted for grain, corn and soybean crops not intended for human consumption, is therefore not possible, including in neighboring Ontario, as are forestry application and industrial composting in the region.
Even restoring mining sites or revegetating an uncultivated environment where nothing grows would require an exemption.
This option could be justified in an already heavily contaminated site, estimates Sébastien Sauvé, professor of environmental chemistry at the University of Montreal.
If it is a wasteland or an old mine and there are already very high levels of cadmium and copper, there is added value in using these products because we provide organic matter, nitrogen and phosphorus. the plants will be able to grow.
Sébastien Sauvé, professor of environmental chemistry at the University of Montreal
However, the transfer of pollutants to the surrounding fauna and flora must be prevented, because what would grow there is “obviously not suitable for consumption,” warns Professor Sauvé.
Biomethanation is ruled out because sludge from aerated ponds, the purification technology used in Rouyn-Noranda, does not produce biogas, the report says.
What is an “aerated pond”?
Aerated ponds are artificial pools in which wastewater is purified through natural biodegradation with the injection of air. The water from the sewer stays there for 15 to 25 days, allowing bacteria and the sun’s ultraviolet rays to reduce the level of contamination. The organic matter settles on the ground and is partially broken down. Ponds should be emptied regularly and the sludge recycled or disposed of. This is the most widely used cleaning technology in Quebec.
The Shadow of the Horne Foundry
In addition to the Viridis Environmental Report, the City of Rouyn-Noranda identifies the Horne Foundry as one of five 1614 non-residential wastewater sources that “have a significant impact on the water being treated” and discloses its Residual Materials Management Plan (PGMR), passed in August – the other four are the landfill, the hospital center and the companies Newalta and Veolia.
PHOTO EDOUARD PLANTE-FRÉCHETTE, LA PRESSE ARCHIVE
One of the chimneys of the Horne Foundry in Rouyn-Noranda
However, the city has “very little data on the quantity and quality” of wastewater from the foundry, this document states – only sanitary water from the foundry is fed into the municipal network, the company treats its own industrial waste water.
“We have an environmental liability here and a soil contamination that no longer needs to be proven,” explained Aurore Lucas, environmental project manager for the city of Rouyn-Noranda, in an interview with La Presse in response to a question about Horne Foundry’s liability.
The contamination likely comes largely from runoff, suspects the city, which, like many in Quebec, is gradually working to separate its storm sewers from its sanitary sewers.
There are a lot of things that can end up down the drain.
Aurore Lucas, environmental project manager at the city of Rouyn-Noranda
This includes the significant releases of atmospheric pollutants from the Horne Foundry that fall to the ground and enter the sewer system through rain.
Without prior characterization of the wastewater, “it is difficult to determine who is responsible.” [de la contamination] and in what proportion,” states Ms. Lucas, who, however, excludes the possibility that residents could excrete these pollutants themselves.
The water that comes from aerated ponds “contains no heavy metals,” assures Ms. Lucas based on regular tests.
Destination Laurentides
Without being able to recycle the sludge from ponds in the urban part of the city, Rouyn-Noranda could send it to the landfills of Sainte-Sophie or Lachute in the Laurentians, the Viridis environmental report suggests.
The latter two, belonging to the multinational waste management, have the necessary capacity and the costs, even taking into account transport, would be lower than those of the Abitibi-Témiscamingue landfills, where the sludge was buried during the 2015 emptying – the city then paid 364 to $394 per ton to bury 1,416 tons of dry sludge at two different locations.
However, this option would be “nonsense” from an environmental perspective, says Karel Ménard, director general of the Quebec Common Front for Ecological Waste Management.
“It makes no sense to drive 1,200 kilometers [aller-retour] to trucks to dispose of sewage sludge, organic matter that produces greenhouse gases in the landfill,” he says.
Rather, the problem must be solved “at the source” in order to reduce the supply of pollutants to the sewage treatment plant, says Mr. Ménard.
In the meantime, the costs of cleaning up municipal sludge should be borne by those who pollute it, says Marc Nantel of the Regroupement Vigilance Mines de l’Abitibi-Témiscamingue (REVIMAT).
“Why isn’t it the foundry? [Horne] Who pays, considering that it is the main polluter of this sludge? “, he asks himself.
In the 2022 dewatering, the sludge was placed in a “geopipe” for dewatering, a process that takes three to five years and at the end of which a decision is made about disposal, according to the city.
“Unusual” case
Rouyn-Noranda isn’t the only city that buries or burns its sewage sludge, but it is one of the few that has to do so because it is too contaminated to be recycled.
PHOTO EDOUARD PLANTE-FRÉCHETTE, LA PRESSE ARCHIVE
A district of Rouyn-Noranda with the Horne Foundry chimneys in the distance
“This is unusual,” explains agronomist Simon Naylor, vice president of development and energy at Viridis Environment.
“This happens in some regions, especially in mining regions,” he says.
According to the latest report from the Société québécoise de Recovery et de Recycling (Recyc-Québec), the municipal sludge recycling rate in Quebec was 57% in 2021.
Montreal burns almost all of its sludge, but this is done primarily to reduce its volume, says the city, which states that the heavy metal content does not exceed the limits prescribed for use as fertilizer – some of the ash so produced also serves as itself agricultural fertilizer.
The city of Quebec also burns its sludge, a decision made in the 1980s to extend the life of its landfill. However, it has committed to gradually adding it to its biomethanation plant, which became operational last spring – which has been possible since Quebec does not use aerated pond cleaning technology.
Pilot project at Horne Foundry
A pilot project to recycle contaminated municipal sludge from Rouyn-Noranda was launched in the summer to test its use in the context of the rehabilitation of a former tailings pond next to the Horne foundry, in collaboration with the city and Viridis Environment. The “deep row trench” technique, which has proven its effectiveness in sand pits with residual clay soils but has never been tested for remediation of mining projects in the north, has been used, foundry spokeswoman Cindy Caouette said. Thousands of trees were planted in ditches filled with contaminated municipal sludge. The aim of the project is to “show that the technique makes it possible to reduce the concentration of problematic elements on the site”, including cadmium contained in the mud, explained Viridis resident Simon Naylor. “If the experiment is conclusive, we will use this technique on several tailings sites when the time comes for remediation,” Ms. Caouette explained.
Quebec is reviewing its legislation
The Quebec government is working on a review of its municipal sludge recycling regulations following a controversy over the import of biosolids from the United States. Some states have banned its use after tests revealed the presence of perfluoroalkyl and polyfluoroalkyl substances (PFAS), commonly known as perennial pollutants, on agricultural lands where it was used. Quebec immediately imposed a moratorium on the importation of this sludge. The government expects the new regulations to come into force in time for the next agricultural season, in spring 2024.
Learn more
2241 Estimate (in tonnes) of the amount of municipal sludge that Rouyn-Noranda plans to recycle
Source: Viridis Environment
794,000 Amount (tonnes) of sewage sludge produced in Quebec in 2021
Source: Quebec Recovery and Recycling Society (Recyc-Québec)
344,000 Amount (tonnes) of sewage sludge “eliminated” in Quebec through incineration or landfill in 2021
Source: Quebec Recovery and Recycling Society (Recyc-Québec)