Aerial view of the Saint-Jérôme plant and aerated lagoons, in 2000

The aerated lagoons allow the plant to process its own wastewater—water used in the papermaking process—and keep from overloading the city’s water treatment system. The suspended matter in the water is decanted and eaten by “good” bacteria. The water that comes out of the lagoons can then be discharged directly into the river, if it meets government standards, or into the sewer system.