August 28, 2008

NATURAL RESOURCES CANADA

The St. Lawrence River in Montreal is a natural waterway at the heart of the city. Montreal is seeking provincial and federal government funding for its new wastewater facilities.

Above is an aerial view of the current Montreal Wastewater Plant, which will soon be replaced with the world’s third-largest ozonation wastewater plant.

Above is the Indianapolis Ozonation Plant, showcasing elements similar to those which will be implemented in Montreal.

Technology

Montreal finalizing plans for $200 million plant using ozonation to treat wastewater

Plant will be built on one of world’s biggest existing ozonation sites

PETER KENTER

correspondent

MONTREAL, QC

The City of Montreal is finalizing plans to build a $200-million ozonation plant to treat its wastewater, one of the largest such facilities in the world.

The facility will be built on the site of the current wastewater treatment plant in Rivière des Prairies, currently the world’s third largest ozonation wastewater plant, treating more than 2.5 million cubic metres of wastewater daily. Ozonation is largely used to treat drinking water, although some smaller cities, such as Indianapolis, already use ozonation to treat wastewater.

The province of Quebec banned the use of chlorine as a wastewater treatment in 1987 because of its harmful effects on marine and plant life. Wastewater is currently treated using a variety of physical and chemical processes before it’s released into the St. Lawrence River near île Ste. Thérèse.

“There are three basic alternatives which are available to treat wastewater,” says T. Duncan Ellison, Executive Director of the Canadian Water and Wastewater Association.

“The traditional one has been chlorine, but the problem is that chlorine forms chloramines when it reacts with any ammonia residual in the wastewater effluent and chloramines are particularly toxic to fish.

“Part of the municipal wastewater strategy of the Canadian Council of Ministers of the Environment is to reduce the use of chlorine and to reduce the potential discharge of chloramines. Another alternative to that is ultraviolet (UV) disinfection which is being used in some parts of the country and a third is ozonation.”

A committee struck in 1997 with representatives of the city’s wastewater treatment department, the Québec ministère du Développement durable, de l’Environnement et des Parcs, and ministère des Affaires municipales et des Régions was charged with the responsibility of analyzing wastewater treatment alternatives and developing an action plan to implement the most viable disinfection process.

Research was conducted by the Institut national de la recherche scientifique and Environment Canada, testing the use of both UV radiation and ozonation to treat wastewater at a miniature “eco-laboratory” at the Montreal treatment plant.

The study determined that ozonation was more effective in removing bacteria, viruses, pharmaceuticals and industrial chemicals from the wastewater stream, and less dangerous to marine life near the wastewater outflow. The committee gave the stamp of approval last November.

The ozonation process involves generating ozone at the treatment plant and using it to break down organic substances by exchanging electrons with them, leaving only oxygen as a by-product. The city already uses ozonation to treat its drinking water.

“Ozone is generated on site using ozone generators supplied with electrical power, and of course, Montreal has access to relatively large quantities of cheap electrical power due to Quebec Hydro,” says Ellison.

“The advantage of using ozone as a disinfectant is that it is also believed to reduce the quantities of pharmaceutical and personal care product residuals in the water. It’s an extremely powerful oxidizer, which causes these chemical residuals to break up and be decomposed.

“Ozonation has really only come into play in the past two or three years as a wastewater treatment, so this project puts Montreal in the category of world leader. From an association perspective, we encourage all cities to make this kind of investment.”

Construction projects will involve modifying the exiting wastewater treatment plant and building ozonation stations, says Richard Fontaine, Director of Wastewater and Sewer Plant at the Montreal facility.

“The exact layout of the new building will depend on the type of ozone injection system that’s considered most effective in our performance tests,” he says.

The city is seeking funding from both the province and the federal government to help build the facility.

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