Grantee Research Project Results
Final Report: Passive Treatment of Metal-rich Waters through Enhanced Wetland Technologies: A Field Scale Pilot Project
EPA Grant Number: R829423E02Title: Passive Treatment of Metal-rich Waters through Enhanced Wetland Technologies: A Field Scale Pilot Project
Investigators: Nairn, Robert W.
Institution: University of Oklahoma
EPA Project Officer: Chung, Serena
Project Period: July 15, 2002 through July 14, 2004
Project Amount: $160,000
RFA: EPSCoR (Experimental Program to Stimulate Competitive Research) (2001) RFA Text | Recipients Lists
Research Category: EPSCoR (The Experimental Program to Stimulate Competitive Research)
Objective:
The overall goal of this research project was to implement a mesocosm column project to examine passive amelioration of contaminated mine waters in ecologically engineered wetland-type ecosystems. We employed a series of replicable mesocosm columns under controlled laboratory conditions to address a poor quality Pb and Zn mine discharge at the Tar Creek Superfund Site in Ottawa County, Oklahoma.
The specific objectives of this research project are to: (1) examine an effective sequence of sequential unit processes; (2) determine the effects of microbial community structure and activity on the dominant anaerobic treatment mechanisms in vertical flow unit processes; and (3) enhance specific treatment processes via optimization. The experimental design includes alternating sequences of three passive treatment cell designs: vertical-flow wetlands, surface-flow wetlands, and vertical-flow limestone cells. The expected results of these efforts are to: (1) evaluate cost-effective and sustainable passive treatment technologies for mine drainage pollution abatement at hard rock mine sites; (2) utilize biogeochemical performance data to design targeted sequential treatment systems in an effort to elevate passive treatment technologies research to the next-generation; and (3) stimulate substantial reductions in chemical exposure at mining sites.
Degraded surface and ground water quality are major environmental concerns at many active and abandoned mining sites. Passive treatment technologies (i.e., those that rely on natural biogeochemical and microbiological processes to ameliorate mine drainage problems) provide a viable treatment alternative at abandoned sites.
The mine discharges are amenable to passive treatment through a series of coupled aerobic and anaerobic unit processes. Previous work on net alkaline waters has demonstrated that oxidation and hydrolysis (aerobic mechanisms) are the most effective means of Fe removal. Subsequent trace metal (Pb, Zn, and Cd) removal is completed most effectively via a combination of bacterial sulfate reduction and carbonate formation under elevated partial pressures of CO2 (anaerobic processes). Therefore, the experimental design included aerobic oxidation cells, organic matter-based anaerobic cells, and anaerobic limestone cells in the unit process train.
The Oklahoma Strategic Improvement Plan (SIP), in association with a Science and Engineering Environmental Research (SEER) project, seeks to improve the competitiveness of Oklahoma researchers to successfully compete for and conduct research in environmental management systems, site remediation, life-cycle assessment, and environmental monitoring. Researchers at three research universities (Oklahoma State University, University of Oklahoma, and University of Tulsa) collaborated in an interdisciplinary study of enhanced life-cycle assessment that incorporates human health risk assessment, dynamic economic impact assessment, and sociopolitical assessment into the standard life-cycle assessment protocol. The test of this enhanced protocol was conducted at Oklahoma’s largest Superfund site. The technology evaluated for enhanced life-cycle assessment was funded as a SEER project conducted at this site. The technology involved the use of engineered wetlands to remove heavy metals from surface water seeps emanating from abandoned mines.
Summary/Accomplishments (Outputs/Outcomes):
Vertical flow treatment cells appear to depend on bacterial sulfate reduction as the primary pathway for contaminant retention. The laboratory-scale passive treatment system constructed at the University of Oklahoma received simulated mine drainage similar to that discharging at abandoned Pb-Zn mines at Tar Creek. This study evaluated the effects of the sulfate-rich mine drainage on the major microbial groups in the organic matter of the vertical flow system. In addition to water quality analyses, substrate cores were analyzed using the most probable number technique. To allow comparisons, initial populations of sulfate-reducing bacteria, fermentative bacteria, nitrate-reducing bacteria, and Fe-reducing bacteria were enumerated in fresh spent mushroom compost. The analyses demonstrated that sulfate-reducing bacteria showed the greatest population increase, followed by fermentative bacteria and Fe-reducing bacteria. An overall decrease, however, in the population of nitrate-reducing bacteria was observed. The findings from this study aid understanding of the response of microbial communities to the sulfate-rich mine drainage.
Journal Articles:
No journal articles submitted with this report: View all 1 publications for this projectSupplemental Keywords:
Superfund, site remediation, life-cycle assessment, LCA, wetlands treatment, heavy metals, heavy metals removal, engineered wetlands, Tar Creek, Oklahoma, OK, mine discharge, passive wetlands, water treatment, lead mines, zinc mines, water contaminants, science and engineering environmental research,, RFA, Scientific Discipline, Geographic Area, Water, Water & Watershed, Environmental Chemistry, State, Ecology and Ecosystems, Watersheds, biogeochemical study, wetland restoration, constructed wetlands, water quality, Oklahoma (OK), construction and design of wetlands, groundwater, metals, mining impacted watershedProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.