This project focuses on an acid mine drainage biological sulfate reduction technology. Aqueous waste contained in the shaft and flowing through the tunnels of the Lilly/Orphan Boy Mine are being treated using the mine as an in situ bioreactor. A substrate composed of cow manure, wood chips, and alfalfa was added in 1994 to promote growth of the sulfate-reducing bacteria (SRB). The mineshaft extends to a depth of 250 feet, and it has been flooded to the 74-foot level for over 50 years. This is the level of the portal tunnel. Figure 4 shows a cross-section of the underground mine with the technology installation detailed.
In 2005, this field demonstration was in its eleventh year. The analytical data generally demonstrates a decrease in dissolved metals concentrations within the mine tunnel. Manganese, however, is not removed because SRBs are not effective in its removal. The plot indicates that there is a significant increase in dissolved metals concentrations during a spring runoff; however, the levels decreased when flow rates returned to normal.
The final sampling for this project was conducted in July 2005. This sampling also included retrieving a sample from the shaft in situ bioreactor for characterization of the microbial community. This information will be included in the final report along with an economic evaluation of the technology.