Selenium from power plants poses ecological risks, spurs EPA review
By Sarah Coefield
Environmental Health News
December 4, 2009
But the manmade lake, built by one of the world’s largest coal-fired power plants to hold its wastewater, contains high levels of selenium that jeopardize the birds and render fish unsafe to eat.
Selenium is an essential nutrient, but in wildlife and people excess amounts can be dangerous. Now the U.S. Environmental Protection Agency is preparing a new regulation that would require more than 600 coal-fired power plants to clean up — perhaps even eliminate — wastewater discharged into lakes, rivers and other waterways.
The national standards, scheduled to be unveiled in 2012, will replace a patchwork of state regulations that EPA officials say are too lax to protect fish and wildlife from toxic metals and other elements, particularly selenium, in the power plants’ wastewater. Some states allow the plants to emit selenium at levels hundreds of times higher than EPA’s water-quality standards, while others don’t even require monitoring for it.
High selenium levels can deform or kill fish and birds, sometimes even wiping out species.
“For selenium, that boundary between … the optimum amount that you actually need and stepping over that line to toxicity is just a knife edge,” said Marjorie Brooks, an assistant professor in the zoology department at the University of Southern Illinois and co-editor of an upcoming book about selenium in aquatic environments. “We do need to be really vigilant about how much is there and how much is leaching into the system.”
Power plants that burn coal require large volumes of water for their cooling towers so they are typically situated close to lakes and rivers, said C. Richard Bozek, director of environmental policy at the Edison Electric Institute, a trade association of shareholder-owned electric companies.
The EPA has regulated power plant wastewater since 1982 for other contaminants, but regulation of selenium and metals has been left to individual states.
In September, after studying some coal-fired power plants, the EPA concluded that "current regulations have not kept pace with changes that have occurred in the electric power industry over the last three decades.”
The study “revealed significant concerns around metals from discharge from these power plants,” said Mary Smith, director of the engineering and analysis division at the EPA’s Office of Water.
Duke Energy’s Gibson Generating Station is one of many plants that have drawn the attention of environmental agencies. Rather than rely on the nearby Wabash River for its plant, which serves Indianapolis and nearby areas, Duke Energy constructed a 3,000-acre lake in the 1970s to use as a cooling pond and to store its waste.
The lake was closed to fishing in 2007 because selenium concentrations in the fish exceeded levels safe for subsistence fishing.
But bird eggs at the lake contain high selenium levels, which can prevent eggs from hatching, said Scott Pruitt, field supervisor at the Bloomington office of the U.S. Fish and Wildlife Service. Biologists there are trying to determine if the terns’ reproduction is being harmed. So far, no action has been taken under the Endangered Species Act. “You can’t take action over concern,” Pruitt said. “You have to take action over proper scientific evidence.”
To provide an alternative habitat for the birds, the power company in 2008 paid to pipe water from the Wabash River into the nearby Cane Ridge Wildlife Management Area, part of a federal refuge which previously received water from Gibson Lake with unacceptable levels of selenium.
Another contaminant, boron, leached in 2007 from the plant’s ash ponds into the drinking water of a nearby town, East Mount Carmel.
The company has been voluntarily working with federal officials to address the selenium problem, although it contends that the Clean Water Act does not apply to its manmade lake.
“We discharge into our cooling lake as a way to avoid having to release into a natural water body,” said Eric Myers, Duke Energy’s director of environmental health and safety policy. “We actually built that lake.” EPA officials said they have not yet determined whether the lake falls under the jurisdiction of the federal law.
At coal-fired power plants, selenium and metals reach lakes and other water bodies from two main sources: scrubbers, which clean contaminants out of the air, and ash ponds, which store waste from coal combustion, Smith said.
While scrubber wastewater is sometimes stored, reused or evaporated to a disposable sludge, it can also be treated in a settling pond and then released into a nearby waterway. Water from ash ponds can overflow in a storm or be siphoned off to a water body to prevent the pond from losing its structural integrity. Ash pond wastewater can also leach into surrounding soil and threaten groundwater.
Selenium occurs naturally in coal, and is especially prevalent in bituminous coal, which is burned mostly in the eastern United States.
Once in the water, selenium can start causing problems.
It builds up in animal tissues, so animals higher up the food web end up with more in their systems. Selenium poisoning caught national attention in the 1980s when agricultural runoff was responsible for a massive wave of bird deformities and fish kills in the Kesterson National Wildlife Refuge in California.
Severe selenium problems caused by power plants date back to the 1970s.
Duke Energy’s Belews Lake Steam Station in North Carolina began discharging ash pond effluent into Belews Lake in 1974. After just four years, the selenium had eradicated all but a single species of native fish, the mosquitofish, and two non-native ones, said A. Dennis Lemly, a research professor of biology at Wake Forest University in Winston-Salem, N.C..
In 1985, the power plant switched to dry waste disposal. The selenium concentrations in the fish declined dramatically, but the fish were still being harmed ten years later. Although recent fish counts showed that diversity returned to normal, no one has looked for other ecological effects.
“The question I have is what are the selenium concentrations in those fish and is there any residual effect that might have been in the sediments and incorporated into the food chain after all these years?” Lemly said.
Also, fish downstream of a West Virginia coal-fired power plant accumulated selenium and metals in their tissues, according to another study by Lemly.
“Coal ash poses a hazard no matter where it is or how it’s disposed of,” he said.
The lack of federal oversight has led to spotty regulations across the nation. State agencies set limits on power plant wastewater on a case-by-case basis, and the states don’t all monitor the same contaminants.
“Most power plants lack effluent limits or monitoring for the pollutants EPA has identified as warranting attention,” Enesta Jones, an EPA spokeswoman said in an e-mail. “There is no state that regulates all the pollutants of concern from all of their power plants.”
ECHO, indicate that few power plants even monitor for selenium, and of those that do, most discharge it at concentrations far greater than the 5 ppb. The standard is not enforceable at power plants since it applies to lakes and streams, not discharge.The EPA recommends selenium concentrations in water stay below 5 parts per billion to protect aquatic life. But records in an EPA online database called Enforcement and Compliance History, or
Pennsylvania permits the EME Homer City Generator power plant to discharge selenium concentrations 320 times greater than the EPA’s standard. And even with one of the most generous discharge limits in the region, the plant violated its permit nine times over the past three years, according to the EPA database. It has never been fined under the Clean Water Act, although the company was fined $200,000 by Pennsylvania in 2007 for violating the selenium limits.
Discharge permits provided by states typically let power plants have more contaminants in wastewater than would be considered safe for aquatic life because they allow for dilution. But some experts say that dilution is not a viable solution for protecting fish and wildlife.
“It sets up essentially a trap for fish and wildlife in an area where they can be exposed to extremely high concentrations. So it’s kind of a loophole,” Lemly said.
“Dischargers are able to dump in a much higher concentration in the hopes that it will be diluted, and the EPA, on the other hand, is hoping that dilution will take care of the concentration and allow it to come down to meet their water quality criterion,” he added.
Power plants spray scrubbers to reduce contaminants that cause acid rain—a process that cleans the air but can spell trouble for the aquatic environment.
“If you run water through your scrubber system, you’re not making the selenium disappear, you’re just transferring it from going into the air and moving it into the water,” Brooks said.
“You may end up with a reservoir that’s got very, very high concentrations…It’s got to be sequestered,” she said.
Smith of the EPA said simply sequestering the wastewater in ponds is unlikely to solve the problem. “Birds and other wildlife are attracted to these treatment ponds where they store the waste,” she said.
Instead, the EPA may prohibit coal-fired power plants from discharging wastewater altogether, Smith said. That would force major changes in the industry.
Of the more than 600 coal-fired power plants in the country, only a fraction is classified as zero liquid discharge. Power plants in Illinois don't discharge any scrubber wastewater. Instead, they evaporate it and landfill the solids. Other power plants, particularly in the Southwest, achieve zero discharge by evaporation.
Duke Energy is in the process of converting one of its ash ponds at the Gibson plant to dry ash by 2013 and closing it by 2020. Another will continue to handle liquid waste.
The burden a zero liquid discharge standard would pose to the industry is impossible to predict, said Bozek of the Edison Electric Institute. Every power plant is different, he said.
But odds are it won’t come cheap.
“There’s a cost component to this idea of changing out things,” said Ed Legge, a media representative for the institute. “There always is.”
The EPA will take that cost into consideration, Smith said. “We’ll aim for the one that gives us the best reduction that’s affordable,” she said. .
The industry worked closely with the EPA as it carried out its study and will continue to take part in the discussion, Bozek said. But, he said, suggestions that wastewater has gone unregulated are “false”.
“Even if something is not dealt with explicitly in the guidelines, that does not mean it is not regulated,” Bozek said. Individual power plants work with the states to determine what contaminants to monitor, he said. And the list frequently includes metals that have so far gone unregulated by the EPA.
Meanwhile, financial and technical issues will likely keep power plants from cleaning up wastewater before the EPA finalizes its new regulations in 2014.
“It’s premature and not necessarily a good business decision to guess what the EPA is going to do,” Bozek said.