Untreated sewage spills, like the recent spill into Shediac Bay, may become more common, according to a University of New Brunswick biologist.

Michelle Gray, an assistant professor with the department of forestry and environmental management, said aging infrastructure could make overflows more possible.

"The reality is across Canada, and across our region, we have a lot of aging infrastructure in terms of the sewage and the water piping," said Gray.

"A lot of these things were put in place decades ago and they're sort of coming to end of life or near end of life."

During heavy rain on Aug. 18, about 18,500 litres of untreated wastewater flowed into Shediac Bay.

An E. coli test at nearby Parlee Beach released the next day showed a dramatically increased count, or enough bacteria in the water to force a no swimming advisory.

While the time period suggests a link between the overflow and the increased E. coli numbers, the Department of Health couldn't confirm this was the case.

"It is difficult to conclusively identify specific point and non-point sources," said a department spokesperson, referring to a 2017 pollution study of the beach.

"Surface water run-off from agriculture and urban areas, sewage system overflows, on-site sewage disposal systems, and birds, wild and domesticated animals are potential sources."

Untreated contaminants

Michelle Gray, an assistant professor with the department of forestry and environmental management at the University of New Brunswick, says untreated sewage could contain trace contaminants. (CBC)

Gray said the troubling thing about the overflow was that since the water was untreated, it's unclear what was in the water.

"Untreated sewage could have trace contaminants," she said.

"The sewage pipes tend to gather things from domestic, but maybe even some industrial outflows. There could be some trace metals or trace contaminants that haven't been taken care of through the sewage treatment."

Gray said an increase of E. coli in the water could harm organisms living in the bay because the bacteria would use up oxygen that would normally be saved for the native organisms.

However, water quality history in Shediac Bay could mean the organisms there are somewhat immune.

"The resident biota might have already adapted and we [may] have a pollution-tolerant community that's been established there," said Gray.