Industrial discharges into Quebec waterways: a 50% reduction that largely went unnoticed
Suspended solids discharged by Quebec's major industries into waterways dropped by half between 2006 and 2023. This improvement was driven 87% by the pulp and paper sector, historically one of the province's biggest polluters.
Total suspended solids discharged by Quebec industry (t/year)
The surprising figure
Suspended solids (TSS) are solid particles - fibres, clay, metallic residues - that remain suspended in water and disrupt aquatic ecosystems by reducing light penetration and clogging fish spawning habitats. Data from Quebec's Industrial Discharge Reduction Program (PRRI), which has tracked roughly 200 industrial sites since 1996, shows a clear trend: from 2006 to 2023, total TSS released by major industries fell from 18,400 to 9,200 tonnes per year - a drop of nearly 50%.
This did not happen by chance. The PRRI, launched in 1988 and extended to the pulp and paper sector in 1993[1], operates through five-year ministerial authorizations with progressively tightened requirements for each establishment. In 2022, of the 89 regulated sites, 69 were subject to requirements at least as strict as the base provincial standards[7].
The pulp and paper sector's dominant role
The pulp and paper sector alone accounts for 87% of industrial TSS discharged in 2023 - 8,033 tonnes, down from 17,112 tonnes in 2006, a 53% reduction. Two mills drive this picture: Smurfit WestRock in La Tuque (formerly WestRock), which in 2022 released 1,084 tonnes of TSS while treating over 39 million m³ of effluent[3], and Domtar in Windsor, with 923 tonnes of TSS that same year[3].
Process modernization played a role. In 2017, WestRock La Tuque received $10 million from Quebec's EcoPerformance program to upgrade its pulp washing and bleaching operations[11]. Mill closures also contributed: between 2006 and 2023, several Quebec pulp mills shut down - Donnacona (2009), Hull/Gatineau (2011), Matane (2012), then Amos and Baie-Comeau (2020-2021)[10][2]. The respective share attributable to closures versus efficiency gains remains difficult to quantify.
This trend mirrors a national pattern. According to Environment Canada, TSS releases from Canadian pulp and paper mills fell from 80,200 to 46,100 tonnes between 2006 and 2022 - a 42.5% drop despite relatively stable production[3].
Top 8 industrial sites — average annual TSS (t/year, 2006-2023)
Forty years of regulatory effort
This progress is part of a long-term effort. In the late 1970s, virtually all of Quebec's industrial effluents were discharged untreated[4]. Between 1981 and 1995, the pulp and paper sector had already cut its TSS by 78%[4]. The Quebec Pulp and Paper Mills Regulation (Q-2, r. 27), adopted in 2007 and regularly updated[5], sets discharge limits in kg of TSS per tonne produced, with stricter standards for mills built after 1992. A complementary federal regulation has been in force since 1992[6].
Investment continues. In December 2024, the Domtar mill in Saint-Félicien - another Quebec pulp mill - launched a new biological wastewater treatment technology, the first industrial use of this system in the province[8]. In 2025, Quebec launched the PREP program with $15 million to help pulp mills reduce their water consumption[9].
What the data does not show
A 50% reduction in TSS does not mean the end of impacts on receiving water bodies. Environmental Effects Monitoring studies conducted under the federal program show that effluents from 70% of Canadian mills still affect fish populations and habitats, despite meeting existing standards[12]. The federal regulation is currently under revision to address these findings.
The PRRI program also covers only large establishments under ministerial authorization. Discharges from small and medium-sized industrial operations are not included in this dataset, which limits the scope of the picture.