Merde most foul: Montreal begins controversial 8-billion-litre raw sewage dump into river

Montreal, Canada's second-largest city, began dumping untreated sewage into the St Lawrence River on Wednesday, angering environmentalists with a repair operation that could release as much as 8 billion litres of effluent 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 create a greater environmental hazard if it unexpectedly broke.

The action prompted outrage from cities and citizens downstream - worried about raw sewage in the water and the possibility of detritus such as condoms washing up on riverbanks. Even some upstream were concerned because of the precedent it was setting.

“It's surprising, disgusting and outrageous that the city of Montreal took this path, which is the least costly alternative for them,” said Lee Willbanks, from advocacy group Save the River, based in the riverside town of Clayton in New York state. “If Montreal does it, others municipalities might do the same.”

Signs advising against touching the water were posted on the banks of the river directly opposite Montreal's main port area. Despite the large size of the dump, waste will likely be quickly diluted and swept away by the huge volume of the river and there was no odour or physical signs of the operation, which has generated the Twitter hashtag #flushgate.

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.”