Montreal Plans to Use Ozonation to Disinfect All Wastewater

Montreal is seeking help from the provincial and federal governments to add a $200-million ozonation facility to its current treatment plant, The Gazette reported.

Montreal plans to disinfect all its wastewater using ozonation, a technology that uses ozone to remove bacteria, viruses, pharmaceutical drugs and industrial chemicals.

"We are proposing an innovative solution that will make Montreal a leader in waste-water disinfection," Montreal Mayor Gérald Tremblay said as he announced the plan Jan. 30.

Montreal's wastewater treatment plant in Rivière des Prairies is currently the third largest in the world, behind only Seoul's and Hong Kong's in terms of the amount of water treated, the newspaper reported.

The plant removes suspended solids and phosphorus in wastewater using various chemical and physical processes, and then pumps that water back into the river near île Ste. Thérèse, at the northeastern tip of the island.

For the last decade, however, environmental groups and communities downstream from the plant have been demanding Montreal also disinfect the wastewater, in light of increasing evidence that some of the substances released into the river cause illness and disease or act as endocrine disruptors, the newspaper reported.

Montreal invested in equipment to disinfect wastewater using chlorine in the mid-1980s. But in 1987, the provincial environment department banned the use of chlorine for wastewater treatment, because of its harmful effects on marine and plant life.

In the early 1990s, the Montreal wastewater treatment station and its various partners began studying the possibility of using two different chlorine-free processes--ozonation and ultraviolet radiation. A committee of representatives from the plant, the provincial Environment Department and the Municipal and Regional Affairs Department was given a mandate in 1997 to analyze the current research, conduct pilot projects and recommend the best disinfection method for Montreal.

That committee concluded that along with being more effective than ultraviolet radiation in eliminating bacteria, viruses and harmful chemicals, ozonation also was less harmful to marine life, the newspaper reported.

Pilot projects conducted in the $2-million "eco-laboratory" at Montreal's treatment plant showed that ultraviolet radiation killed fish and other marine life close to the outflow at a higher rate than that of ozonation, according to the newspaper.

Water-treatment experts stressed that study results could be applied only to Montreal's wastewater, explaining that the results probably depend on the specific type of chemicals being released in the area. Montreal has a heavy concentration of pharmaceutical companies.

The mayor noted that Montreal cannot afford to build the ozonation plant without funding help from the province and the federal government. But he said he expects the city to be responsible for only 15% of the cost, as the province generally funds about 85% of municipal water treatment projects, the newspaper reported.

"Montrealers are not the only ones who will benefit," Tremblay said. "This is a project for all of Quebec, especially all the communities along the St. Lawrence River."

A few other cities, like Indianapolis, use ozonation to disinfect wastewater, but Montreal will be the first to disinfect great volumes of water using this method.

Source: The Gazette