|
|
|
 |
 National Science
Foundation Award #0540593 |
 |
|
|
Preventing Pyrite Oxidation: A Geomicrobial Strategy for Source Control of Acid Mine Drainage |
| |
| Investigator(s): |
JoAnn Silverstein (PI)
; Harihar Rajaram (Co-PI)
|
| Sponsor: |
University of Colorado at Boulder, CO 80309 3034926221
|
| Start Date/Expiration Date |
2005-07-01 to 2006-06-30 (amended 2005-06-27) |
| Awarded Amount to Date: |
$95,409 |
| Abstract: PROJECT SUMMARY
Acid mine drainage (AMD) is the contamination of water by acidity, iron, sulfate and heavy metals leached from waste rock by chemical and bacterially catalyzed oxidation of pyrite minerals and other sulfidic source rock. There are an estimated 45 billion tons of waste rock in abandoned mine sites in the United States alone, resulting in pollution of thousands of kilometers of streams and aquatic habitat and a significant loss of biodiversity (General Accounting Office, 1996). Current technologies for remediation of AMD sites and secondary contamination areas are costly and cause further environmental disruption (e.g., excavation and removal, addition of lime). Moreover, many of these sites are small and dispersed over mountainous terrain; so that many streams are impacted before a large treatment process such as a reactive barrier or wetland can be installed. At low pH, pyrite-oxidizing bacteria - typically acidophilic, autotrophic, and aerobic strains such as Acidithiobacillus ferrooxidans -- catalyze acid generation. Research is proposed to investigate the hypothesis that pyrite oxidation may be inhibited at the rock-water interface by enhancing the growth of native populations of heterotrophic bacteria, which will consume oxygen and release organic constituents that are able to complex metals, trap precipitates and, eventually, give rise to alkalinity-generating reactions such as anaerobic Fe(III) and sulfate respiration, blocking reactive sites and enabling long-lasting site restoration.
Intellectual Merit. This exploratory research project aims to understand the coupling of
microbial community structure and fundamental biogeochemistry at the rock-water interface with flow and transport processes through waste rock formations. Experiments at scales of a single rock fragment and waste-rock columns will be conducted to test whether addition of biodegradable organic substrate will result in a shift in the dominant bacterial populations from autotrophic to heterotrophic metabolism that, in turn, will impact oxygen consumption, iron and sulfur cycling and metal leaching. We will also investigate the influence of hydrologic variables (e.g. formation saturation conditions, water detention time) and rock properties (e.g. porosity, pyrite fraction) on the effectiveness of heterotrophic bacterial growth and inhibition of AMD generation. In addition to understanding the interrelations between rock media, drainage flow, the microbial community, and geochemical reactions, our experiments will enable quantification of the carbon required to inhibit bacterial pyrite oxidation and evaluate the long-term sustainability of the biogeochemical changes caused by carbon addition. A mechanistic reactive transport model will be developed to quantify fundamental microbial-geochemical-hydrologic processes at the single rock scale and provide a framework for upscaling to the rock column and field scales. This model will be used to design carbon addition and remediation strategies for pilot field-scale applications.
Broader Impacts. It has been estimated that there are over 100,000 abandoned mine sites in the
Western US producing acid mine drainage. The engineering application of the results of this research will be a novel cost-effective process for long-term remediation of acid-generating waste rock by localized addition of a benign soluble organic substrate. There will be associated benefits to the habitat and to local communities in AMD-impacted watersheds enabling recreation, tourism, and reliable water resources. Because the process design envisioned is based on fundamental biogeochemical and flow processes, such a remediation strategy could be modified for application at a variety of acid-generating field sites. AMD is a topic of significant public concern in Colorado and other mountain states with historic mining activity. There are two local stakeholder groups in watersheds with significant AMD discharges that already have ties to researchers at the University of Colorado and have expressed interest in sustainable site restoration methods that minimize disruption of their communities and can be implemented at low cost. However, at this time, too little is understood about both the fundamental mechanisms of the proposed restoration method to attempt field-scale applications. The results from this exploratory research would allow a field trial of carbon addition and enable collaboration of university researchers, mining companies, public land agencies, and residents in AMD impacted watersheds. Finally, the faculty investigators are committed to involving a diverse student population in research activities by participating in research programs for underrepresented minority students at the University of Colorado, Boulder such as the Colorado Diversity Initiative in Science, Math and Engineering. |
|
| NSF Org: |
BES - Division of Bioengineering & Environmental Systems |
| Award Number: |
0540593 |
| Award Instrument: |
Continuing grant |
| Program Manager: |
Cynthia J. Ekstein
BES Division of Bioengineering & Environmental Systems
ENG Directorate for Engineering
|
| NSF Program(s): |
ENVIRONMENTAL ENGINEERING |
| Field Application(s): |
Trace Contaminants, Water Pollution |
| Program Reference Code(s): |
TOXIC SUBSTANCES/SOLID & HAZARDOUS WASTE, 9187 |
| Program Element Code(s): |
1440 |
|
|
| |
 |
|
|
|
|
|
|
|
