By Yang Zhang and Rachael Gleason
Dec. 18, 2009
Burning coal is dirty business. The fuel is laden with heavy metals such as mercury and arsenic and chemicals that cause acid rain. When power plants burn coal, they release the contaminants into the air. Over the past couple of decades, increasingly stringent air pollution standards have forced power plants to clean up their dirty air.
The universal solution? Scrubbers that use a spray of water to trap air pollutants.
But scrubbers don’t really solve the pollution problem. They just move it somewhere else, and that movement is starting to cause problems, particularly as federal regulators consider tough new regulations on water pollution from power plants.
Hatfield’s Ferry in southwest Pennsylvania is among many coal-fired power plants battling legal concerns over displaced pollution.
The Environmental Integrity Project, an organization that advocates for more effective enforcement of environmental laws, sued the plant’s parent company, Allegheny Energy, in 2005 for persistent air pollution violations.
As part of the settlement, company officials agreed to use scrubbers to limit air emissions. They expect the devices, installed earlier this year, to cut acid rain-causing emissions by approximately 95 percent.
But the scrubbers create toxic wastewater, which Hatfield’s Ferry is permitted to release into the Monongahela River — a drinking water source for more than 90,000 people.
“What’s happening is that the toxics in the air are simply being transferred into the waters,” said Jennifer Peterson, an attorney with the Environmental Integrity Project.
The plant exceeded permitted wastewaster discharge levels 23 times in the past three years, according to U.S. Environmental Protection Agency data. That’s more than most power plants throughout the Great Lakes region.
So last March, officials with the Environmental Integrity Project formally requested the Pennsylvania Department of Environmental Protection repeal Hatfield’s Ferry’s discharge permit. Allegheny Energy filed its own request with the agency to weaken discharge standards.
Hatfield’s Ferry is not alone. Many power plants are turning to scrubbers to comply with tough federal air pollution regulations.
Approximately 25 percent of coal-fired power plants, most of which are more than 30 years old, currently use scrubber technology, according to the American Society of Mechanical Engineers. The number increased significantly since wastewater guidelines were last revised in 1982.
A coal-fired power plant in Monroe, Mich., recently became the first in the state to use scrubbers. Officials at Monroe Power Plant are preparing to install additional systems to the tune of $600 million, according to its parent company, DTE Energy Co.
The EPA predicts more than 60 percent of coal-fired capacity will use scrubbers to reduce air emissions by 2020.
“We are expecting to see the number of scrubbers to continue to increase pretty substantially,” said Ron Jordan, project manager for the revised steam electric power generating effluent guidelines revision at the EPA’s Office of Water. “That means new wastewater streams will be generated at power plants that don’t have scrubbers right now or an increase of wastewater at power plants that might have another new scrubber.”
HOW SCRUBBERS WORK
Scrubbers work much like air fresheners.
They spray a water and limestone mixture to absorb contaminants such as sulfur dioxide and mercury from the air.
The EPA is particularly interested in metals like selenium, arsenic and mercury, Jordan said.
“When we figured out where those metals are coming from, we tend to focus more on scrubber wastewater,” he said.
But the metals don’t have to stay in the water. Some plants use settling ponds and chemicals to separate toxic particles. Others use microorganisms to consume organic contaminants, according to an EPA study released in October.
Tougher regulations will prevent wastewater pollution from scrubbers altogether, said Peterson, the attorney with the environmental project.
As part of its rule-making process, the EPA is considering prohibiting power plants from discharging polluted wastewaster, said Mary Smith, the director of the engineering and analysis division at the EPA’s Office of Water. This will push plants to invest in new technologies that eliminate wastewater.
More than one fifth of the 491 coal-fired power plants studied by the EPA have scrubbers. Of those with scrubbers, 31 don’t discharge any wastewater.
There are three coal-fired power plants in Great Lakes states that eliminate wastewater discharge by completely recycling water within the scrubber system: Ameren’s Duck Creek in Canton, Ill., Xcel Energy’s Sherburne County in Becker, Minn. and General James M. Gavin in Ohio.
Duke Energy’s Gibson Generating Station in Indiana treats scrubber wastewater by removing heavy metals and settling out the pollutants before injecting the treated water into a salt-water aquifer 10,000 below ground. The pollutants are transferred to storage ponds that discharge into the power plant’s man-made lake.
Power plants can also eliminate scrubber wastewater by using evaporation ponds and mixing the scrubber wastewater with dry fly ash, according to the EPA report.
But that doesn’t mean it’s easy. Or cheap.
Power plants are hesitant to invest and maintain expensive technologies, according to Frost & Sullivan, a service that studies the market for water treatment in the power industry.
The EPA will take cost into account as it prepares new wastewater regulations, Smith said.
“If zero discharge has got a technology and is affordable, that’s what we would aim for,” she said.
Sarah Coefield contributed to this report.