Pitt Researchers Undertake $1.06 Million Federal Project to Curtail, Reuse Harmful Wastewater From Marcellus Shale Drilling
Pitt’s approach will harness problematic acid mine drainage for use as a sanitizer and supplemental water source in natural gas extraction process
The U.S. Department
of Energy recently selected the University of Pittsburgh as one of nine
national partners that will develop techniques for curtailing the possible
environmental and health hazards associated with tapping the massive natural
gas reserves lying beneath Pennsylvania and surrounding states. Roughly 70
percent of Pennsylvania sits atop the Marcellus Shale formation, which experts
estimate contains up to 500 trillion cubic feet of natural gas with about $500
billion worth of recoverable gas.
Researchers in Pitt’s Swanson School of Engineering will lead a three-year,
$1.06 million project to better manage the wastewater generated by the
extraction process used on the Marcellus Shale. Difficult to treat, the
wastewater usually languishes in reservoirs or the environment. The Pitt
approach calls for a new method that would allow the water to be safely reused
in gas wells that would contain extraction costs, limit the byproducts flowing
into the environment, and reduce the strain on freshwater sources currently
tapped during extraction. Furthermore, the researchers seek to tackle the
problem of acid mine drainage—the environmentally damaging water flowing from
old mines—by using it as a sanitizer and supplemental water source.
“Our approach is to not only reuse the wastewater, but also reduce the level of
treatment it requires prior to being reused, which should be a much more
economical approach,” said Radisav Vidic, chair of the Swanson School’s
Department of Civil and Environmental Engineering and a William Kepler
Whiteford professor. “And by reusing the acid mine drainage readily available
at many gas drilling locations, we can manage acid mine drainage from older
mines and wastewater from current drilling operations, both of which are
serious environmental concerns.”
Vidic heads the project with Eric Beckman, codirector of Pitt’s Mascaro
Center for Sustainable Innovation and the George M. Bevier professor of
chemical and petroleum engineering. They will work with Carnegie Mellon
University assistant professor Kelvin Gregory. The National Energy Technology
Laboratory (NETL)—the lead research and development office for the U.S. energy
department’s Office of Fossil Energy—will contribute more than $794,000 to the
effort, and Pitt will provide around $269,000.
The technique for mining the Marcellus Shale is known as hydraulic fracturing.
A high-pressure mix of local-source freshwater, sand, and various chemicals
known as “slicking agents” fractures the rock formation and allows trapped gas
to escape. One gas well can consume 2 million to 5 million gallons of fluid
with 25 to 100 percent of it returning to the surface as wastewater, or
“flowback.” Flowback contains varying levels of hydrocarbons, heavy metals,
natural radioactive materials, and very high levels of total dissolved solids
(TDS). TDS includes such substances as calcium, potassium, sodium, chloride,
and carbonate; Marcellus Shale flowback tends to have much higher
concentrations of TDS than wastewater from other hydraulic fractured sites.
In Pennsylvania, flowback—which can have five times the salinity of seawater—is
typically stored in reservoirs or trucked to a brine treatment plant. But
current treatment processes cannot remove the majority of TDS, so many of these
substances typically end up in surface water. In their project proposal, the
Pitt team refers to a 2008 incident when treated flowback released into the
Monongahela River resulted in TDS levels exceeding safety limits set by the
Pennsylvania Department of Environmental Protection. The department restricted
the amount of flowback treatment plants could receive, which halted some
drilling operations in Western Pennsylvania.
To contain flowback pollution and freshwater consumption, Vidic and Beckman
will first develop new slicking agents that would be stable in high-salinity
water. These chemicals would allow for the flowback to be reused in adjacent
gas wells without extensive off-site purification. Then, they will study the
use of locally available acid mine drainage to further treat the flowback and
simultaneously supplement the freshwater supply. Finally, the cleaner flowback
would be pumped back into the gas well, reducing the strain on freshwater
sources and curtailing costs of shipping and storing wastewater. The project
will consist of a research phase and a subsequent field-demonstration phase.
Pitt is the only Pennsylvania institution granted a project. The eight other
projects include ALL Consulting in Tulsa, Okla.; General Electrical Company;
West Virginia University; the University of Arkansas; the Ground Water Protection
Research Foundation in Oklahoma City; the Geological Survey of Alabama; Altela
Inc. in Albuquerque; and the Texas Engineering Experiment Station.
There is always newsworthy research and events happening in the Swanson School of Engineering.
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