HALIFAX -- A pulp mill in Nova Scotia that has come under fire for exceeding pollution limits plans to challenge a new industrial permit that calls for tighter restrictions on emissions and water consumption.

Bruce Chapman, general manager at the Northern Pulp mill near Pictou, says the new five-year provincial permit is unacceptable because it threatens the long-term viability of the mill.

"It really goes beyond where the standard is for much of the industry," he said in an interview on Friday.

The regulations "don't put us on a level playing field with other mills," said Chapman, who declined to be more specific.

The company says implementing the new rules could cost Northern Pulp about $90 million.

"We are committed to improving our environmental footprint, but this doesn't allow us to maintain a sustainable business," Chapman said.

Earlier, Environment Minister Randy Delorey said the permit responds to concerns raised by residents of Pictou County, some of whom have complained for years about the stench coming from the mill at Abercrombie Point.

"The new approval demonstrates that the status quo is no longer an option," he told a news conference.

Delorey said the permit brings the plant in line with similar operations in North America.

The changes would be phased in over five years, but other critics say it appears there is confusion over how much water the mill uses and when it will be required to comply with new pollution caps.

"For the premier to say that they're going to get tough on this facility ... he's not going to be able to keep his promise," said Matt Gunning, a member of the citizens group Clean the Mill.

The permit says the mill is using about 95,000 cubic metres of water per day, a figure that must be reduced to 67,500 cubic metres by 2020 -- a 34 per cent reduction.

But Gunning said mill officials told the group in November that it actually uses only 78,000 cubic metres daily, which means the five-year target would amount to a tiny reduction.

Chapman wouldn't comment on how much water the mill uses.

Karla MacFarlane, the local Progressive Conservative legislature member, also cited the smaller water usage figure, suggesting the government officials aren't sure about their numbers.

"So once again it's showing that they're incompetent," she said.

Delorey said there were no water limits in the previous permit.

The new permit also says the mill must reduce particulate emissions to about five times lower than levels set in the previous permit.

When the emissions from the mill's recovery boiler were tested in 2013, they were found to be 78 per cent higher than acceptable standards. The company has said it has reduced its emissions since then and has promised to start up new pollution-control equipment in May.

Northern Pulp must also reduce the daily release of waste water effluent into nearby Boat Harbour by 25 per cent by 2020. And it has been ordered to develop a plan by 2017 to stop run-off and other chemicals from flowing into the polluted body of water.