Biological Control of Acid Mine DrainageEPA Grant Number: U914934
Title: Biological Control of Acid Mine Drainage
Investigators: Marchand, Eric
Institution: University of Colorado at Boulder
EPA Project Officer: Packard, Benjamin H
Project Period: January 1, 1996 through January 1, 1999
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1996) RFA Text | Recipients Lists
Research Category: Fellowship - Environmental , Academic Fellowships , Safer Chemicals
The objective of this research project is Tto prevent or mitigate the formation of acid mine drainage (AMD) by supplementing acid-producing mineral formations with organic carbon substrate to enhance the growth of heterotrophic microorganisms. Results of this work will be used to assess whether a change in the microbial ecology can lead to a reduction in the amount of toxic metals leached into the aquatic environment from AMD sites.
To better characterize the interactions between autotrophic and heterotrophic bacteria under organic carbon amended conditions, laboratory-scale experiments have been performed using cultures of bacteria indigenous to acid-producing sites. BecauseSince a significant number of mine sites experience subsurface flow of water through a system of fractures and cracks within ore formations, this research is investigating the interactions among autotrophic and heterotrophic bacteria along preferential flow paths, as well as in porous mineral systems. It is believed that an increase in the heterotrophic bacterial population within a fracture will limit transport of oxygen, thereby inhibiting the growth of autotrophic microbes and resulting in a cessation of acid production. There are two mechanisms by which this may occur: (i1) a fast-growing heterotrophic biofilm covers Thiobacillus. ferrooxidans cells, preventing oxygen diffusion to the autotrophs; and (ii2) preferential growth of heterotrophic bacteria at the fracture inlet consumes oxygen, inhibiting autotrophic growth down gradient. Changes in the microbial ecology of these systems will be monitored using sensitive chemical and microbiological measurement techniques. In order tTo assess the spatial variability and activity of microbial species within the fracture biofilm, 16S rRNA oligonucleotide probes labeled with fluorescent dyes will be used, giving insight into the microbial community changes that occur when heterotrophic bacteria are encouraged to grow in AMD environments.