By Christinne Muschi
MONTREAL, Nov 11 (Reuters) - The Canadian city of Montreal began a controversial dump of untreated sewage into the St. Lawrence River early on Wednesday, angering environmentalists with a repair operation that could release as much as 8 billion liters (2.1 billion gallons) of wastewater into a major waterway.
The city has said the dump, expected to last up to a week, is necessary while work is carried out to replace ageing parts of the waste treatment system that could unexpectedly break and create a greater environmental hazard.
In full-page ads in Quebec's main newspapers on Wednesday, Montreal Mayor Denis Coderre defended the operation as vital to protecting the river in the long run.
"As I have repeatedly said, if there were better options we would certainly have considered them," he said. "But the reality is that the option we have chosen is the one with the least environmental impact."
The operation was delayed until after Canada's federal election in October. The new environment minister, Catherine McKenna, imposed extra conditions including monitoring, improved clean-up plans, and regular reporting of water quality through mid-2016.
Still, there was consternation among some in the city of 1.6 million, and surrounding areas.
Parti Quebecois provincial legislator Mathieu Traversy said several municipalities feared their riverbanks would be polluted with "diapers, condoms and syringes."
"Who will pay for the cleanup?" The Montreal Gazette quoted him as asking.
The city has said the dump will have little effect on the river's fish population and will not affect drinking water quality for residents.
The vast St. Lawrence River connects the Great Lakes to the Atlantic Ocean. In some parts it forms the border between Canada and the United States, so the operation has worried some in the United States.
U.S. Senator Charles Schumer, a New York Democrat, had tried to get the U.S. environmental regulator to stop the discharge, media reported. New York state borders Canada on the other side of the St. Lawrence but is upstream from Montreal.
Alexandre Joly, head of a non-profit group devoted to improving the quality of water in St. Lawrence and access to it, called on Montreal residents to avoid putting some items such as condoms and tampons down the toilet during the wastewater dump.
He also urged people to limit water use by washing dishes in a basin instead of with running water, and to use biodegradable soaps.
"You have to remember that whatever you put in the toilet for the next week is going to go directly into the river," Joly told the Canadian Broadcasting Corporation. (Reporting by Alastair Sharp in Toronto and Randall Palmer in Ottawa; Editing by Frances Kerry)
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