T11 PM Developments in Bioremediation of Acid Mine Drainage Wastes
Tuesday, 15 November 2005: 1:50 PM - 5:30 PM in 343-344

(JEN-1117-753919) The Effect of Water Saturation on Carbon Addition for Pyrite Oxidation Inhibition.

Jenkins, J¹, Silverstein, J¹, ¹ University of Colorado Boulder, Civil Environmental Engineering, Boulder, CO, USA

ABSTRACT- A strategy for remediation of acid mine drainage (AMD) sources is initiation of a shift in microbial populations from dominance of pyrite oxidizing bacteria to iron and sulfur reducing microorganisms by the addition of biodegradable organic matter. However, hydrologic conditions in waste rock formations are expected to play a major role in determining substrate availability, redox conditions affecting iron and sulfur transformations, as well as contaminant transport. Experiments were conducted using two 37.8-liter tanks packed with 0.1 to 10-cm rock particles obtained from a mine waste pile near Leadville, CO resulting in 50% bulk porosity in the tanks. Drainage water was recirculated through the tanks with addition of fresh deionized water to obtain a 9-day average hydraulic residence time. One tank was run under saturated conditions and the second was run with trickle flow to achieve 16% saturation. The headspace of both tanks was sparged with air continuously. Production of soluble ferric iron (Fe(III)) and sulfate in the unsaturated tank was significantly higher than in the saturated system. The unsaturated tank generated 16 g/L ferric iron and pH of 1.5 compared with 0.1 g/L ferric and pH 2.5 in the saturated tank. After acid generating conditions were established, glucose was added to the tanks at a rate of 36 g/day as C. The effect of water saturation and carbon addition in inducing a microbial population shift to iron and sulfur reduction was evaluated by water chemistry monitoring, including pH, iron speciation, sulfate, and redox, and as well as microbial population monitoring. Most Probable Number (MPN) technique for autotrophs and heterotrophs, Fluorescent In-Situ Hybridization with labeled small sub-unit rRNA probes for indicator genera: Acidithiobacillus, Acidiphilium, and Leptospirillum, and DNA extraction and sequencing were used to evaluate the bacterial populations. Results indicate that drainage flow controls the availability of organic matter and oxygen, and in turn bacterial activity and production of acid mine drainage.

Key words: Acid Mine Drainage, Carbon Addition, Water Saturation, Leptospirillum Ferrooxidans