The Environmental Protection Agency announced Monday it will set stricter requirements for how coal-fired power plants dispose of wastewater full of arsenic, lead and mercury — a major source of toxic water pollution in rivers, lakes and streams near electric generators across the country, from Wyoming to Pennsylvania.

In a new rulemaking process that kicked off Monday, President Biden’s team is aiming to undo one of the Trump administration’s major regulatory rollbacks. Last year, the Trump EPA weakened rules forcing many coal plants to treat wastewater with modern filtration methods and other technology before it reached waterways that provide drinking water for thousands of Americans.

“What we found is that the Trump administration’s 2020 rule really is lacking,” Radhika Fox, the EPA’s top water official, said in an interview Monday. “We think that we can do better when it comes to reducing water pollution from coal power plants.”

The power plant wastewater rule is among dozens of Trump administration rollbacks the Biden team is seeking to reverse in its effort to tackle climate change and reduce pollution that often overburdens the poorest communities in the United States.

“It’s just so illegal, what the Trump administration did,” said Thom Cmar, an attorney with the law firm AltmanNewman. He is representing environmental groups that sued the Trump EPA over its power-plant wastewater rule. “Our hope was that the Biden EPA, because of its commitment to climate change, to environmental justice, to protecting clean air and water, would see that this was a no-brainer.”

It is also an example of how the Biden administration is grappling with decades of neglect on water issues under Democratic and Republican presidents as it pushes for billions of dollars from Congress to replace lead pipes and fix aging sewage systems.

Yet the decision upset some environmental advocates who say the Biden team is not working fast enough. The EPA will not try to revert immediately to the stricter standards set under President Barack Obama in 2015, allowing the weaker Trump-era rule to remain in effect.

That means many coal plants will be allowed to send polluted wastewater into rivers and streams for several more years while the agency writes the new regulations. The EPA expects to propose new requirements on power plants’ wastewater by next fall, with a finalized rule expected by the end of Biden’s term at the latest.

Brett Hartl, government affairs director at the Center for Biological Diversity, said the Biden administration should have asked a federal appeals court to strike down the weaker Trump-era wastewater rule.

“If their timeline is 2024, that’s four years of damage,” he said. “The industry is getting the better end of the deal out of this.”

The Biden EPA saw a legal risk in asking a court to pull the Trump administration’s wastewater rule too quickly, because doing so could end up forcing the agency to revert to even more-outdated pollution standards written four decades ago.

“Really, our rationale around that is that otherwise these coal power plants would be operating under very outdated 1982 regulations,” said Fox, the EPA water chief. “So essentially what we’re doing today through this action is we’re locking in near-term progress.”

During the first five months of 2021, about two dozen coal-fired generators throughout the country — including multiple plants in Indiana, Michigan, North Carolina, Pennsylvania and Tennessee — asked regulators to lock in permits under the looser requirements for cleaning up wastewater, according to the Sierra Club.

Among those power stations is the Cumberland Fossil Plant in Tennessee, one of the largest coal-fired units in the country, which received a broad exemption for certain wastewater treatment methods under the Trump-era rule. The plant, operated by the federally controlled Tennessee Valley Authority, is upstream of popular fishing spots in the Cross Creeks National Wildlife Refuge.

“The thing that is so insidious about this is that the TVA is an extension of the administration,” said Stephen Smith, executive director of the Knoxville, Tenn.-based Southern Alliance for Clean Energy.

TVA spokeswoman Ashton Davies said that, as a federal agency, the utility “meets or exceeds all federal regulations and timelines at each of our facilities.”

Katie Sweeney, executive vice president at the National Mining Association, said her group, which represents coal-mining companies, is pleased the Trump-era rule will remain in effect for now. “While disappointed that the new administration has decided to reconsider the 2020 rule,” she said, “we look forward to engaging with EPA.”

Power companies, meanwhile, are hoping to have a role in shaping how the EPA ends up regulating their power plants.

Quin Shea, vice president for environment, natural resources, and occupational safety at the Edison Electric Institute, which represents investor-owned electric utilities, said it “looks forward to working with the U.S. Environmental Protection Agency on ways to continue the industry’s clean-energy transformation as the agency works to implement the existing technical requirements.”