Maine’s Department of Environmental Protection is launching a new permit system that requires discharges by cruise ships to be as clean as wastewater treated on shore.

Cruise ships will be prohibited from dumping wastewater within three miles of shore unless they can meet the same water quality standards as municipal treatment plants.

“We have pretty sweeping authority,” said Pam Parker, co-leader of the DEP’s cruise ship program. “This is the first waste discharge license for cruise ships in the United States, if not the world.”

The rules apply to passenger ships that have at least 500 beds.

From the point of view of the cruise ship industry, Maine’s initiative will have little impact, said Christine Fischer, spokeswoman for the International Council of Cruise Lines.

Fischer said council members, who include more than 90 percent of the cruise market in North America, already have agreed not to discharge wastewater within four miles of the nation’s coastline.

“The cruise ships are already doing this on their own,” she said.

Charlie Phippen, Bar Harbor’s harbor master, said Thursday that 78 cruise ships carrying approximately 100,000 passengers are expected to visit the seaside resort town in 2006. The Queen Mary 2 and the Queen Elizabeth 2, each of which can carry around 3,000 passengers and crew, are expected to be among those that drop anchor offshore from the town and Acadia National Park.

Phippen said he does not expect the new rule to affect local cruise ship visits because Bar Harbor already has let cruise line operators know it has a “zero-tolerance” policy for discharging effluent in its anchorage.

“They all say they go at least four miles offshore before they dump anything,” Phippen said. “A lot of them go farther than that, up to 12 miles out.”

Phippen said the town has tested water in Frenchman Bay around anchored cruise ships and found only one relatively small vessel that discharged anything in the bay other than engine-cooling water. That discharge was within then-acceptable state limits, he said, but the ship’s operator promised local officials not to dump any waste in the town’s anchorage again.

Still, he said local leaders unofficially support the new DEP rule.

“I don’t think anybody on the coast of Maine has a problem with it,” he said.

Joe Payne of Friends of Casco Bay said that despite existing industry practices, the rules are significant because the state no longer will depend on voluntary guidelines to protect its waters.

“Now Maine is in control,” he said. “We are in the driver’s seat, and we have standards.”

The U.S. Environmental Protection Agency is expected to designate Casco Bay as a no-discharge zone this winter, putting the bay off-limits for any sewage discharges from tankers, freighters and cruise ships, as well as any pleasure boats equipped with on-board toilets.

Cruise ships brought a record number 45,225 passengers to the port of Portland in 2005. But as the passenger count is going up, the number of visiting cruise ships is going down.

Twenty-nine ships stopped in Portland this year, down 45 percent from the peak year of 2001, according to Jeff Monroe, the city’s transportation director.