Montreal’s raw sewage — ozone relief in sight

After years of research, the city of Montreal has decided that ozonation is the disinfection technology it should use to treat its wastewater.
In early February, the city accepted the recommendations of a tri-partite expert committee that it should add ozonation facilities to its existing sewage plant at the east end of Montreal on the Ile-aux-Vaches. Currently the plant handles between 2.5 million cubic metres of wastewater a day, about half of Quebec’s wastewater.
The existing plant only screens the raw sewage before it is released into the St. Lawrence River. Chlorination disinfection was stopped in the late 1980s because of concerns of its impact on the aquatic fauna.
Since then the city has been investigating the problem. It set up a laboratory to study the effects of the wastewater on the ecology of the river, working in association with the INRS-Armand Frappier scientific research centre of the University of Quebec and Environment Canada’s St. Lawrence Centre. This research was combined with a pilot project to determine the advantages and disadvantages of ozone and ultraviolet disinfection, and their effects on the aquatic fauna. The pilot tests were conducted since 2005. No consulting engineering firms were involved.
Now the city has to submit the recommendation of the committee to a standing committee on urban development and a public hearing in the winter of 2008.
The estimated cost of adding the new facilities is approximately $200 million, and they will will cost around $9 million to operate. Before any plans for construction can go ahead, the city awaits funding support from the province.