Although notorious illnesses like cholera and typhoid fever are now largely unknown in the U.S., each year this country continues to clean up water that has been contaminated by hazardous waste. At Purdue, Civil Engineering’s Suresh Rao (shown below left, with a doctoral student) applies the study of environmental hydrology and environmental chemistry to water-quality issues, assessing the impact of agricultural and industrial operations on the quality of our water supplies.
Crop and animal production practices can contaminate streams and rivers with nutrients, pesticides, pathogens, and veterinary pharmaceuticals, says Rao, the Lee A. Rieth Distinguished Professor of Environmental Engineering. Industrial waste sites can include dry-cleaner sites, gas stations, manufacturing plants, and military bases. “We’ve developed new, innovative technologies for cleaning up these sites better,” he says, and for thus helping to clean up contaminated groundwater beneath them.
As chair of the National Research Council’s Committee on Innovative Remediation Technologies in the 1990s, Rao participated in a national assessment for developing recommendations on federal action needed to boost toxic-waste cleanup. (He later co-chaired an EPA-appointed panel of international experts to examine new approaches for evaluating cleanup of contaminated sites.) During his time on the NRC committee, he says, “it became apparent that one of the constraints to adopting new technologies is that the goals, or end points, as prescribed by regulatory agencies cannot be achieved. The goals are so stringent that at a reasonable cost and timeline, people couldn’t afford to get there.” As a result, proven technologies were not being adopted.
The NRC’s 1997 committee report projected that total costs over the following 75 years would climb to between $500 billion and $1 trillion. To help industry make the most of its cleanup dollars, Rao is working with colleagues at the University of Florida, Clemson University, the EPA, and the Air Force Institute of Technology on research projects funded by the Department of Defense to identify performance metrics and to develop performance assessment tools and guidelines. The goal is to develop a risk-based and economically rational framework for better technological options for cleaning up contaminated sites.
What’s crucial, the researchers have found, is to determine and to take into consideration the mass of contaminant leaving a waste site per day. That’s the mass “loading.” Rao and his colleagues have patented a method by which to measure, in the field, the loading that occurs at a site.
“The source could be an old tank that’s leaking solvents—gasoline or dry-cleaning fluids,” he says. At military sites, the contaminants are typically industrial solvents used to clean engine parts at a maintenance facility. “Leaking from tanks or the disposal of used solvents in trenches creates a source zone in which there are very high concentrations of contaminants that dissolve over long periods of time—decades, centuries—and cause extensive groundwater contamination that is difficult to clean up,” says Rao.
The source area can be as small as a professor’s office or as large as an entire building, but the contaminant leaving the source can generate a plume of up to hundreds of meters long or, in some cases, a kilometer in length. Cleaning up the source prevents future contamination and shrinks the plume that’s already there, which might be affecting someone’s water supply or discharging into a wetland or stream.
Rao and his colleagues have conducted field research at U.S. military bases, including Fort Lewis (an Army installation in Washington), Port Huememe (a Naval base in California), Hill Air Force (near Salt Lake City), and other defense facilities where used solvents from decades past had been disposed of in trenches or barrels, a standard practice at the time.
Rao is also collaborating with colleagues in Australia to test the utility of the new site assessment technology. “We do computer modeling, we do laboratory research, we do field work at the defense sites,” he says. “Our work has morphed from fundamental research to technology development to policy development.”
The approach the researchers have developed is finding increasing acceptance among their scientific peers and is slowly being adopted by the user community. “If we don’t adopt these kinds of innovative approaches,” says Rao, “we’ll pay a price in increased contamination and the postponing of cleanup to future generations.”