Robert Nairn, Ph.D., Professor in the School of Civil Engineering and Environmental Science, and Director of the Center for Restoration of Ecosystems and Watersheds, University of Oklahoma
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ABSTRACT
Solving global water challenges requires a revolution in our thinking of the relationship between humanity and the Earth. Twentieth-century solutions – based on “gray” infrastructure driven by fossil fuels – cannot sustainably address the complexity and interrelatedness of the 21st century problems we face. Natural infrastructure approaches, based on the principles of Ecological Engineering, hold promise for a resilient and sustainable water future. Mining and mineral processing represents one of the most dramatic human influences on water resources. A case study of natural infrastructure performance in a drastically disturbed mining watershed demonstrates the utility of this approach through application of a thorough understanding of naturally occurring biogeochemical and ecological processes leading to water quality improvement and habitat restoration.
Surface and ground waters in the Tar Creek (Kansas-Oklahoma) watershed of the Tri-State Lead-Zinc Mining District were deemed to be degraded due to “irreversible man-made damages” 40 years ago, an administrative decision resulting in minimal efforts to address risk from legacy pollution. Artesian flowing mine waters, from an 80,000-acre-foot (26 billion gallon) mine pool, and substantial tailings pile (covering several thousand acres) leachate and runoff contribute elevated ecotoxic metals concentrations to receiving streams. Despite more than four decades as a US Environmental Protection Agency Superfund Site, Tar Creek remains listed on the state’s Clean Water Act 303(d) List of Impaired Waters. Two full-scale, ecologically engineered mine water passive treatment systems (PTS) were installed to address some of these source waters, contaminated by elevated concentrations of iron, zinc, lead, cadmium, arsenic and other constituents. The Mayer Ranch PTS (since 2008) and Southeast Commerce PTS (since 2017) produce circumneutral pH, net alkaline effluents containing ecotoxic metals concentrations meeting in-stream water quality criteria. Each PTS includes multiple process units designed for specific biogeochemical functions. Iron is primarily retained via oxidative mechanisms in aerobic ponds and wetlands. Resulting iron oxyhydroxide solids retain trace metals (especially arsenic) via sorption. Primary lead, zinc and cadmium removal occurs in sulfate-reducing vertical flow bioreactors. Annually, MRPTS and SECPTS collectively retain approximately 84,000 kg of iron, 5,500 kg of zinc, 30 kg of lead, 27 kg of arsenic, and 12 kg of cadmium. The receiving stream has demonstrated substantial water chemical composition improvement and ecological recovery, with documented increases in both fish species richness and abundance, as well as the return of other fauna, including North American beaver and river otter.
BIO
Robert W. Nairn, PhD, BCES, is an Environmental Scientist with more than 35 years of professional experience in government, academia, consulting. and the non-profit sector. A western Pennsylvania native, he is a first-generation college graduate from a family of steelworkers and coal miners. He holds a B.S. from Juniata College and was employed as a Research Biologist with the U.S. Bureau of Mines Pittsburgh Research Center before completing a Ph.D. at The Ohio State University (with University of Florida alumnus William J. Mitsch). He serves as the Robert W. Hughes Centennial Professor of Engineering, David L. Boren Distinguished Professor, and Sam K. Viersen Family Presidential Professor in the School of Civil Engineering and Environmental Science and Director of the Center for Restoration of Ecosystems and Watersheds (CREW) at the University of Oklahoma. He is also a Director of the Water Technologies for Emerging Regions (WaTER) Center and an adjunct professor of Biological Sciences. His research team emphasizes the understanding of naturally occurring biogeochemical and ecological processes in natural infrastructure to address water challenges.
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