Wastewater in Rouyn-Noranda | Too contaminated to be recycled

Rouyn-Noranda’s wastewater contains so many heavy metals that the sludge coming from wastewater treatment infrastructures in the urban part of the city cannot be recycled. A rare situation in Quebec, which forces the City to bury them at great expense, possibly hundreds of kilometers away.

Cadmium and copper, metals emitted in large quantities by the Horne Foundry, are found there at levels that exceed the thresholds authorized to be used as fertilizer, just like arsenic, to a lesser extent, indicates a report from Viridis environment dated July 2021, that The Press obtained.

The firm specializing in the management of fertilizing residual materials attributes the presence of these metals “to the regional background noise of the soil and to anthropogenic activities [c’est-à-dire d’origine humaine]surrounding the city.

Viridis environment had been mandated by the City to find “possible solutions aimed at valorizing municipal biosolids” – which are rich in organic matter, nitrogen, phosphorus and trace elements such as iron, magnesium and manganese.

“The study of the file does not allow us to identify recovery solutions [permises] », However, concludes the firm. The document lists options, all of which would require special authorization from Quebec’s Minister of the Environment.

Agricultural spreading, which is usually permitted for cereal, corn and soybean crops not intended for human food, is therefore not possible, including in neighboring Ontario, as is forestry spreading. and industrial composting in the region.

Even the restoration of mining sites or the revegetation of an uncultivated environment, where nothing grows, would require an exemption.

This option could be justified in the case of an already heavily contaminated site, estimates Sébastien Sauvé, professor of environmental chemistry at the University of Montreal.

However, it would be necessary to prevent the transfer of contaminants to the surrounding fauna and flora, since what would grow there would “obviously not be suitable for consumption,” warns Professor Sauvé.

Biomethanization is ruled out because sludge from aerated ponds, the purification technology used in Rouyn-Noranda, does not generate biogas, the report indicates.

The shadow of the Horne Foundry

In addition to the Viridis environment report, the City of Rouyn-Noranda identifies the Horne Foundry as one of five non-residential sources of wastewater, out of 1614, which “have a significant impact on the water to be treated”, indicates its Residual materials management plan (PGMR), adopted in August – the other four being the landfill site, the hospital center as well as the Newalta and Veolia companies.

The City, however, has “very little data on the quantity and quality” of wastewater coming from the foundry, it indicates in this document – ​​only sanitary water from the Foundry is sent into the municipal network, the company treating its own industrial water.

“We have an environmental liability here and soil contamination which no longer needs to be demonstrated,” explained in an interview with The Press Aurore Lucas, environmental project manager at the City of Rouyn-Noranda, in response to a question on the responsibility of the Horne Foundry.

The contamination probably comes largely from runoff, supposes the City, which, like many others in Quebec, is gradually working to separate its storm sewers from its sanitary sewers.

Included in the lot are the significant releases of atmospheric contaminants from the Horne Foundry, which fall to the ground and which the rain carries into the sewers.

Without upstream characterization of wastewater, “it is difficult to determine who is responsible [de la contamination] and in what proportion,” says M^me Lucas, who however excludes that residents could excrete these contaminants themselves.

The water that comes out of aerated ponds “does not contain heavy metals”, assures M^me Lucas, based on tests that are carried out regularly.

Destination Laurentides

Without being able to recycle the sludge from the ponds in the urban part of the city, Rouyn-Noranda could send it to the landfill sites of Sainte-Sophie or Lachute, in the Laurentians, suggests the Viridis environment report.

The latter two, which belong to the multinational Waste Management, have the necessary capacity, and the cost would be lower, even taking into account transport, than those of the Abitibi-Témiscamingue landfill sites, where the sludge had been buried during the 2015 emptying – the City then paid $364 to $394 per ton to bury 1,416 metric tons of dry sludge in two different sites.

This option would, however, be “nonsense” on an environmental level, believes Karel Ménard, general director of the Quebec Common Front for Ecological Waste Management.

“It doesn’t make sense to drive 1,200 kilometers [aller-retour] to trucks to dump sewage plant sludge, organic matter which will create greenhouse gases in the landfill,” he says.

Rather, the problem should be resolved “at the source,” in order to reduce the supply of contaminants to the wastewater treatment plant, says Mr. Ménard.

In the meantime, the costs of eliminating municipal sludge should be borne by those who contaminate it, says Marc Nantel, of the Regroupement Vigilance Mines de l’Abitibi-Témiscamingue (REVIMAT).

“Why isn’t it the Foundry? [Horne] who pays, given that it is the major polluter of this sludge? “, he asks himself.

During the 2022 drain, the sludge was placed in a “geotube” to be dewatered, a process that takes three to five years, at the end of which a decision will be made on how to dispose of it, the City says.

“Uncommon” case

Rouyn-Noranda is not the only city to bury or incinerate its sewage sludge, but it is one of the few to have to do so because it is too contaminated to be recycled.

“It’s unusual,” explains agronomist Simon Naylor, vice-president responsible for development and energy at Viridis environment.

“It happens in some regions, especially in mining regions,” he says.

The recycling rate of municipal sludge was 57% in Quebec in 2021, according to the most recent report from the Société québécoise de recovery et de recycling (Recyc-Québec).

Montreal incinerates almost all of its sludge, but it does so mainly to reduce its volume, indicates the City, which specifies that the levels of heavy metals do not exceed the thresholds prescribed for their use as fertilizer – part of the ashes thus generated also serve as agricultural fertilizer themselves.

The City of Quebec also incinerates its sludge, a choice made in the 1980s to extend the life of its landfill site, but it has undertaken to gradually send it to its biomethanization plant, which came into operation last spring – which is possible since Quebec does not use aerated pond purification technology.