Montreal major polluter of St. Lawrence as E. coli plumes drift to Trois-Rivières, study finds

High concentrations of E. coli bacteria colonies are entering the St. Lawrence River in the Montreal area and following the current as far as Lake Saint-Pierre and Trois-Rivières, a recent study found.

"In Montreal, in some places, there's up to a million E. coli colonies per 100 milliliters of water. The current standard for swimming is 200 colonies per 100 milliliters," said François Guillemette.

He's an associate professor of environmental sciences at the Université du Québec à Trois-Rivières who specializes in the ecology of the St. Lawrence. The study was conducted aboard the school's Lampsilis research vessel, and it found that Montreal is a major river polluter.

That's because the city does only a preliminary treatment of sewage, removing the solids but not disinfecting the water before releasing it back into the river. 

Flowing plumes of E. coli can lead to beach closures, as swimming in high concentrations of the bacteria can lead to serious illness. 

But it's not just the E. coli that's of concern. The bacteria is usually an indicator that other microbial pathogens are present, Guillemette said.

These microbes, which include bacteria and viruses, can cause different infections and diseases, he explained.