U.S. EPA has sent a proposed rule aimed at curbing discharges of polluted water from power plants to the White House for review.

The agency agreed to tighten rules on power plants' discharges of arsenic, lead, chromium, mercury and other toxins under a consent decree with advocacy groups the Environmental Integrity Project, Defenders of Wildlife and the Sierra Club in 2010. The rules have not been updated since 1982.

After several delays, the rules are now scheduled to be issued by April 19 and finalized by May 22, 2014, under an agreement struck last month with the environmental groups (Greenwire, Dec. 12, 2012).

"We're hopeful that we'll see a strong rule because the technology is clearly there to reduce or even eliminate these discharges in some cases," said Jennifer Peterson, an attorney with the Environmental Integrity Project.

EPA pointed to coal-combustion wastewater as particularly harmful in a 2009 report on power plants' discharges.

"The total amount of toxic pollutants currently being released in wastewater discharges from coal-fired power plants is estimated to be significant and raises concerns regarding the long-term impacts to aquatic organisms, wildlife, and human health that are exposed to these pollutants," the agency wrote. "Many of these impacts may not be realized for years due to the persistent and bioaccumulative nature of the pollutants released."

The heightened regulation would likely drive up electricity bills, though, as plants moved to install the necessary pollution controls.

Industry group the Utility Water Act Group, which tried to intervene in the environmental groups' lawsuit, said in a recent court filing that impacts on its members "would be concrete and particularized, immediate, and causally related to this lawsuit."