Questions are being raised about the disposal of fracking waste water in Windsor after millions of litres of water were put through the town's sewage treatment plant.

Don Beatty, Windsor's Director of Public Works, told CBC News in an email that more than seven million litres of the water went through the town's sewage treatment plant between March 2010 and August 2011.

The water was processed and then pumped into the Minas Basin.

Nova Scotia's Minister of Environment Sterling Belliveau confirmed the water was analyzed by a consultant and deemed safe, but it wasn't tested for radioactivity.

Belliveau said the consultant wasn't aware of Nova Scotia's geology but as soon as the department became aware of radioactive levels, it issued a stop order to the town.

Millions of litres of water have been used in hydraulic fracturing in the province. Some of it is in holding ponds in Kennetcook and Noel, still more currently sits at storage ponds owned by Atlantic Industrial Services in Debert.

More than two years ago, AIS asked the town of Windsor to dispose of fracking waste water.

Belliveau said even though the water was never tested for naturally occurring radioactive materials or NORMs, the levels were low.

"To me they were low levels … my understanding was low levels and not harmful to the environment or human health, and again I want to point out that this is no longer being processed."

Municipal wastewater plants not designed for fracking

Hydraulic fracturing, or fracking, involves blasting a mixture of water, sand and chemicals into a well bore to split the surrounding rock and release trapped hydrocarbons, usually natural gas, coal bed methane or crude oil.

"There's a chemical cocktail that makes fracking possible. The companies will tell you only one per cent is chemical — but it's what's in those chemicals," said Ken Summers, a member of the Nova Scotia Fracking Resource and Action Coalition.

"Sewage treatment plants are not designed to be able to take out the kind of chemicals that are in fracking waste. They're just not designed for it."

Summers said that NORMs occur commonly throughout the province, but what's not common is the concentration of NORMs that is brought up to the surface during hydraulic fracturing.

"It's not naturally occurring all around us to the degree that it comes out of those shale beds 3,000 metres down," Summers said. "So the water picks up all of this radioactivity, and know it's sitting there in the lagoon, and then lots of it is put into the Windsor sewage treatment plant."

"What's important is that this raises the importance of the review of dealing with fracking," Belliveau said.

"This is something that's very complex and is something that Nova Scotians want to understand, including government. We have committed ourselves to having a thorough fracking review which will be completed in 2014."

The minister told CBC News he's not aware of fracking water being disposed of at any other sewage treatment plants.

He said it was a previous government that issued hydraulic fracturing permits and his government is currently working hard to assess the industry and what's best for Nova Scotia.