Four scientists at the University of New Brunswick say they have water-related concerns if hydraulic fracturing is used to extract shale gas in the province.

The professors, who have released an opinion paper called Potential Impact of Shale Gas Exploitation on Water Resources, say the risks to groundwater from seismic testing are minimal.

But there are problems involving the large amount of fresh water required for hydro-fracking in New Brunswick and the treatment needed for waste water, according to the report.

Tom Al, a hydrogeologist at the University of New Brunswick and one of the study's authors, spoke to CBC News about the difference between common fracking practices in the U.S. compared to Canada.

"Injection in the U.S. is very common, that's because their geology is quite well suited and they have a fairly mature oil and gas industry," Al said.  "I think the geology here in New Brunswick, it remains to be seen whether that could be done because you need deep, highly permeable aquifer systems in saline environments and it's not clear that we would have that."

The researchers contend alternatives to hydro-fracking, using liquefied carbon dioxide or petroleum gas, should be studied.

Hydro-fracking should not go ahead unless there's an environmentally-responsible plan to dispose of the waste water, they said.

Annie Daigle is a hydrogeologist with the province's Natural Gas Group told CBC news fracking wastewater has already been treated at a facility in Debert, Nova Scotia and says hydraulic fracturing is nothing new to the province.

"It's all part of what we've been already been looking at and nothing new there," said Daigle.

In the hydro-fracking process, companies extract petroleum using a pressurized mix of water and other substances injected into shale rock formations or coal beds.

That high-pressure mix creates or widens fissures in the rock, so gas or oil can escape from pores and fractures.

Opponents of the process say it could have a negative effect on local water supplies.

Stephanie Merrill of the Conservation Council of New Brunswick says the study reinforces concerns her organization has been raising.

"We haven't seen this information being presented in this way before," Merrill said.

"It's a huge question mark, I think that we've identified from day one – that this process is inherently contaminating and it produces a lot of toxic waste water. What are we going to do with it? How is it going to be handled, stored, trucked, treated and returned to the environment?"

The UNB researchers estimate the amount of fresh water needed for hydro-fracking is the equivalent of between eight and 24 Olympic-size swimming pools per well.

Careful regulation of the effects on water wells, streams and lakes will be required, they said.

It's unlikely that fracking will contaminate aquifers, according to the researchers.

But shale deposits do reach the surface in the Albert Mines area, which may require a minimum depth for shale development, they said.

Their main concern is the waste water extracted from gas wells because it's too salty and contaminated to be disposed of at water treatment plants or in streams and rivers.

So far, they're not aware of any way the waste water can be recycled for new wells, they said.

In addition, the geology of the area may not allow the waste water to be injected into deep saline aquifers.

Nevertheless, both of those options should be considered, they said.

The researchers include: Dr. Tom Al and Dr. Karl Butler from the Department of Earth Sciences, Dr. Rick Cunjak from the Department of Biology and Faculty of Forestry and Environmental Management; and Dr. Kerry MacQuarrie from the Department of Civil Engineering.

They have no connection to shale gas development, they said.

The purpose of the seven-page opinion piece was to "provide objective information and unbiased information that will ultimately inform the broader shale gas debate," a news release states.

"Given its research capacity and expertise related to this subject, the University of New Brunswick felt that the time was right for the institution to engage in this ongoing public dialogue."

Last week, Windsor Energy Inc. was granted a five-year lease to continue exploring for oil and gas in southern New Brunswick.

Drilling could begin next year, with government approval, the company's chief executive officer Khalid Amin told CBC news.

Premier David Alward has promised to introduce an environmental protection plan this spring. He wants to impose the continent’s toughest shale gas regulations on companies working in the province, he has said.

The Opposition Liberals, meanwhile, have repeatedly called for a moratorium on shale gas exploration until stronger rules are in place to govern the contentious industry.

The issue of hydro-fracking has caused several headaches for the Alward government in the last year, including numerous protests across the province and a 16,000-signature petition filed by the Conservation Council of New Brunswick, calling on the government to abandon its plans for shale gas exploration.