Thursday, October 2, 2008: 4:00 p.m.
Western Research Institute (WRI) collected water and mine waste material from the Sheldon Mine (Prescott, National Forest, AZ) tailings pile (STP) and waste rock pile (SRP) to conduct laboratory feasibility tests using WRI’s Biological Source Treatment (BST) system for reduction and prevention of acid rock drainage (ARD). In general, the BST system is a site-specific composition of substrate and inoculum amendments designed to grow a hydrophobic, reductive biological barrier over the ARD source material to prevent oxidation of metal sulfides in mine waste materials. Several variations of microcosms with continually saturated source material and source material undergoing wet/dry cycles with different inoculum and substrate amendments were simulated. The pH of the microcosms treated with substrate only and substrate and inoculum was significantly (P ≤ 0.001) higher than control microcosms and microcosms treated with inoculum only for STP, SRP, and CR materials at the end of the 90-day experiments. The pH was not significantly different at the end of the experiment between the substrate only and substrate and inoculum treatments for the STP materials but the pH was significantly (P < 0.001) higher in the substrate and inoculum treatment compared to the substrate only treatment for the SRP materials. This suggests that the indigenous microbial communities in the waste material and substrate may be sufficient for ARD prevention and additional microbial inoculation may not be necessary. Overall, our results indicate that the BST system effectively prevents ARD generation from SRP and STP source material under both saturated and wet/dry conditions.