A decadeslong fight over cleaning up one of the nation's most contaminated riverbeds has posed a difficult question: how to safely remove enough toxic material from New Jersey's Passaic River to fill two MetLife Stadiums.

The federal government is moving forward with long-stalled efforts to rid the Passaic of cancer-causing toxins lodged deep in the riverbed. The U.S. Environmental Protection Agency has proposed dredging 4.3 million cubic yards of sediment and transporting it out of New Jersey for incineration and disposal, at an estimated cost of $1.7 billion.

Now, scientists backed by two of the companies liable for the cleanup want to take the effort in a different direction, with a plan to test whether a form of bacteria could be deployed to neutralize some of the pollution. The group of bacteria, called Dehalococcoides, suck up the hydrogen gas in some carcinogenic chemicals and then leave behind less harmful material, advocates said.

At a cost of several million dollars, the bacteria would be cultivated under appropriate conditions for about 18 months in the river's most polluted stretches, near Newark, and reviewed by two New Jersey universities, said John Pardue, a professor of civil and environmental engineering at Louisiana State University and the proposal's lead scientist.

If the experiment showed success, the technique could be tried on other waterways as a cheaper and less environmentally taxing alternative to dredging, Mr. Pardue said. Dredging is costly and not all environmentalists support it, as it takes resources to transport the material and fills up landfills. "At this scale, developing game-changing technologies would be huge," said Mr. Pardue.