Jennifer West, the groundwater co-ordinator at the Ecology Action Centre, said she has concerns about how Windsor came to accept the fracking waste water. (CBC)

There are calls for more openness in dealing with fracking waste water in Nova Scotia after millions of litres of waste water were put through Windsor's sewage treatment plant.

More than seven million litres of fracking waste 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.

"We've called on them to disclose when waste is being disposed of in this province but the government has refused to do that," said Andrew Younger, the Liberal environment critic.

"Unless Nova Scotians know what is in that waste and what is potentially contaminating our water, then we're at risk."

Sterling Belliveau, Nova Scotia's Minister of Environment, said the water was analyzed by a consultant and deemed safe but it wasn't tested for radioactivity. When the Environment Department discovered the waste water contained radioactive elements, it told Windsor to stop accepting it.

Belliveau said the radioactive levels were low but was unable to say whether they were within acceptable guidelines.

Younger said there's nothing acceptable about what happened.

"I'm very concerned about this. Most treatment plants are not designed to handle fracking waste," he told CBC News.

"They can't handle not only the radioactive active elements but some of the other elements like benzene and so forth that are very often found in fracking waste."

Hydraulic fracturing review expected in 2014

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 and some sits in storage ponds owned by Atlantic Industrial Services in Debert.

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

Jennifer West, the groundwater co-ordinator at the Ecology Action Centre, said she has concerns about how the agreement was reached.

"They're supposed to report what's in the waste water. They're supposed to report everything that they're doing," she said.

"I think this is an example of how self-reporting has a lot of weaknesses."

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.

The Nova Scotia government has delayed a review of hydraulic fracturing until at least 2014.