More than one billion litres of partially treated sewage have flowed into the Red River over the past few weeks, due to a major glitch at a Winnipeg waste treatment plant, according to city officials.

One of the four sewage treatment processes at the South End Water Pollution Control Plant has not been working since Oct. 7, and city staff are stumped as to how and why it broke down.

As a result of the malfunction, effluent coming from the plant — which flows into the Red River — is currently being treated to just 50 per cent of how it would normally be treated, officials said Wednesday.

"Right now we are discharging wastewater to the Red River from the effluent of the plant that is in excess of our license requirement," Mike Shkolny, the city's manager of engineering services, told reporters.

Shkolny said it may sound like a lot of sewage is flowing into the Red River, but he stressed that it's actually a relatively small amount.

He added that it's not raw sewage going into the river, but partially treated sewage.

Biological stage not working

What is malfunctioning is the biological treatment stage, in which microorganisms eat organic material in the sewage.

"For an unknown reason, these microorganisms suddenly stopped thriving on Oct. 7, 2011, upsetting the full biological treatment process," the city stated in a release.

The first two treatment stages — in which grit, sediment and grease are removed from the waste — are working normally.

However, the final ultraviolet disinfection stage is operating at "reduced effort" because the biological treatment stage isn't working, officials say.

Shkolny said city engineers have been unsuccessful in trying to fix the problem so far.

A team of experts has been assembled to work on the issue, but it could be at least another month before they figure out why the treatment process broke down.

Does not meet provincial standards

City officials say this is the first time such a disruption has happened in the history of Winnipeg's sewage treatment plants.

The South End plant, which opened in 1974, treats 60 million litres of sewage a day.

Considering the sewage has been partially treated for the past 26 days, that means more than one billion litres have gone into the river to date.

Shkolny said the problem is not a public health issue, but provincial regulators have been notified because the partially treated effluent does not meet Environment Act licence requirements for the plant.

Fewer people are going in and around the Red River at this time of year, but those who come into contact with the river water should wash their hands thoroughly afterward, he said.

"Full-body contact immersion would not be recommended," Shkolny said.

"However, at this point in time, there's not much recreation going on in the river, so the risk to public health relative to swimming or boating or water-skiing is quite small."

Fishing outfitter surprised

Anyone who catches fish from the river should wash and boil their catch before eating it, he added.

Stu McKay, who owns a fishing outfitting store in nearby Lockport, Man., said the plant malfunction is an example of people's disrespect for water.

McKay said he was surprised to learn that partially treated sewage has been going into the Red River, which runs near his store, Cats on the Red.

"It's amazing, actually, in this day and age that we don't have systems put in place to prevent these types of things [from] happening. I mean, what does it take?" McKay told CBC News.

"Do we not respect water, or should we not be giving it more respect than what we have been in this day and age, knowing that it's the most important resource we have on the planet?"