The federal government has pinned its latest cleanup hopes on a huge new piece of equipment: the world's largest oil-skimming vessel.

The federal government has pinned its latest cleanup hopes on a huge new piece of equipment: the world’s largest oil-skimming vessel.

Officials hope the ship, which arrived in Louisiana on Wednesday, can scoop up to 21 million gallons of oil-fouled water a day. Dubbed “A Whale,” the Taiwanese-flagged former tanker spans the length of 3 ½ football fields and is 10 stories high.

The ship just emerged from an extensive retrofitting to prepare it specifically for the Gulf of Mexico.

“It is absolutely gigantic. It’s unbelievable,” said Ed Overton, a Louisiana State University environmental-studies professor who saw the ship last week in Norfolk, Va.

The vessel looks like a typical tanker, but it takes in contaminated water through 12 vents on either side of the bow. Oil then is supposed to be separated from the water and transferred to another vessel. The water is channeled back into the sea.

But the ship never has been tested, and many questions remain about how it will operate. For instance, the filtered seawater retains trace amounts of oil, so the Environmental Protection Agency will have to sign off on allowing the treated water back into the Gulf.

The Coast Guard will have the final say. The owner, shipping firm TMT Group, will have to come to separate terms with BP, which is paying for the cleanup.

“This is a no-brainer,” Overton said. “You’re bringing in really dirty, oily water, and you’re putting back much cleaner water.

“I don’t know whether it’s going to work or not, but it certainly needs to be given the opportunity.”