Coal is part of our life. It’s an easily accessible and inexpensive fuel that, for many of us, powers everything from the coffee-maker we turn on each morning to the lights we turn on each evening. According to the U.S. Energy Information Administration, coal was the primary source of energy for about 40 percent of electricity generated in the United States in 2011.
But coal is not, by its nature, clean. Mountaintop-removal coal mining contaminates and destroys streams and rivers in downstream watersheds. Burning coal emits carbon dioxide, sulfur oxides, particulates and toxic metals into the atmosphere.
To protect our skies, the U.S. Environmental Protection Agency has established regulations requiring coal-fired power plants to install scrubbers that capture some of these pollutants and reduce the emissions of sulfur and other highly toxic contaminants.
Unfortunately, we may be saving our skies at the expense of our water.
Earlier this month, my research team at Duke University published a peer-reviewed study that found high levels of arsenic, selenium and other toxic contaminants in coal ash residues and wastewater discharges generated by coal-fired plants. We found that these contaminants are getting into the water and sediments of lakes and rivers located downstream from coal ash ponds across North Carolina.
It turns out the EPA-required air pollution scrubbers and other contaminant-trapping technologies used at many power plants, such as fabric-filter baghouses, are keeping many toxic contaminants out of our air, which is good. But the contaminants don’t just disappear. They remain, trapped but largely untreated, in concentrated solid form as coal ash or in liquid form as scrubber wastewater and ash-transport slurries. And they’re accumulating in the lakes and rivers into which the plants directly discharge these wastes.
Some lake sediments in our study contained water with arsenic levels 25 times higher than EPA standards for safe drinking water and twice as high as EPA standards for aquatic life. Arsenic can cause cancer in humans and can kill and cause deformities in aquatic life.
We also detected selenium levels in coal ash wastewaters up to four times higher than EPA standards for drinking water and 17 times higher than standards for aquatic life. Selenium is highly toxic to aquatic life and will cause fish deformities and other growth abnormalities.
Our study showed that some of these toxic contaminants, such as arsenic, are remarkably persistent – they essentially stay with us forever – as they accumulate in the lakes’ sediments and gradually make their way into the entire ecological system.
It’s not just a North Carolina problem. About 600 coal plants generate 130 million tons of coal ash annually in the United States. Of this, around half is stored in settling ponds. The ponds – which numbered around 1,000, at last count – are typically located near rivers and lakes.
Are coal ash contaminants making their way into our drinking waters? Yes, they are. Effluents discharged from coal ash ponds have not been adequately regulated since 1982, which was the last time EPA updated its industrial wastewater standards for these discharges. There are few controls over the type or magnitude of contaminants being discharged from hundreds of coal ash ponds across the nation. None of the monitoring parameters include the toxic contaminants our study found in coal ash wastewaters.
We are at a critical junction: we need to take action. Three years ago, EPA began the process of revising its industrial wastewater standards for steam electric power plants. Coal ash effluents should also be rigorously regulated, using the best treatment that can be afforded.
We have established tools to regulate and protect the air we breathe; it is time for us to also protect our water. Coal will never be totally clean, but we can certainly make it cleaner and eliminate the severe environmental damage our study has discovered.
Avner Vengosh is professor of geochemistry and water quality at Duke University’s Nicholas School of the Environment.