HARRISBURG, Pa. - A drilling technique that is beginning to unlock staggering quantities of natural gas underneath Appalachia also yields a troubling byproduct: powerfully briny wastewater that can kill fish and give tap water a foul taste and odor.
With fortunes, water quality and cheap energy hanging in the balance, exploration companies, scientists and entrepreneurs are scrambling for an economical way to recycle the wastewater.
"Everybody and his brother is trying to come up with the 11 herbs and spices," said Nicholas DeMarco, executive director of the West Virginia Oil and Natural Gas Association.
Drilling crews across the country have been flocking since late 2008 to the Marcellus Shale, a rock bed the size of Greece that lies about 6,000 feet beneath New York, Pennsylvania, West Virginia and Ohio. Geologists say it could become the most productive natural gas field in the U.S., capable of supplying the entire country's needs for up to two decades by some estimates.
Before that happens, the industry is realizing that it must solve the challenge of what to do with its wastewater. As a result, the Marcellus Shale in on its way to being the nation's first gas field where drilling water is widely reused.
The polluted water comes from a drilling technique known as hydraulic fracturing, or "fracking," in which millions of gallons of water, sand and chemicals are blasted into each well to fracture tightly compacted shale and release trapped natural gas.
Fracking a horizontal well costs more money and uses more water, but it produces more natural gas from shale than a traditional vertical well.
Once the rock is fractured, some of the water - estimates range from 15 percent to 40 percent - comes back up the well. When it does, it can be five times saltier than seawater and laden with dissolved solids such as sulfates and chlorides, which conventional sewage and drinking water treatment plants aren't equipped to remove.
At first, many drilling companies hauled away the wastewater in tanker trucks to sewage-treatment plants that processed the water and discharged it into rivers - the same rivers from which water utilities then drew drinking water.
But in October 2008, something happened that stunned environmental regulators: The levels of dissolved solids spiked above government standards in southwestern Pennsylvania's Monongahela River, a source of drinking water for more than 700,000 people.
Regulators said the brine posed no serious threat to human health. But the area's tap water carried an unpleasant gritty or earthy taste and smell, and left a white film on dishes. And industrial users noticed corrosive deposits on valuable machinery.
No harm to aquatic life was reported, though high levels of salts and other minerals can kill fish and other creatures, regulators say.
Pennsylvania officials immediately ordered five sewage treatment plants on the Monongahela or its tributaries to sharply limit the amount of frack water they accepted to 1 percent of daily flow.
"It is a very great risk that what happened on the Monongahela could happen in many watersheds," said Ronald Furlan of the Pennsylvania Department of Environmental Protection. "And so that's why we're trying to pre-empt and get ahead of it to ensure it doesn't happen again."