Operational Lessons Learned During Bioreactor Demonstrations for Acid Rock Drainage Treatment

Abstract

The US Environmental Protection Agency's Mine Waste Technology Program (MWTP) has emphasized the development of biogeochemically-based treatment technologies for mitigation of acid rock drainage (ARD). Progressive technology demonstrations by the MWTP over the past 15 years have resulted in improved operation of sulfate-reducing bacteria (SRB) bioreactors. Although using SRB to treat ARD is now fairly widespread, it was uncommon in the early 1990s when the MWTP used this innovative biotechnology. The first and longest running demonstration was an in situ bioreactor installed within the flooded subsurface workings of the Lilly/Orphan Boy Mine in 1994. The second project, at the Calliope Mine, compared the performance of several SRB bioreactor configurations and operational attributes, including lime pretreatment and reactor temperature. The third demonstration, at the Golden Sunlight Mine, consisted of two treatment steps with a recycle stream. The fourth project was an investigation of existing bioreactor designs and resulted in an improved bioreactor configuration. Significant findings included: (1) a mineshaft could be used as a long-term, in situ bioreactor, (2) SRB thrive in temperature extremes, (3) sulfide recycle effectively avoids contact of ARD with bacterial populations, and (4) ideal bioreactor substrate provides short-term and long-term nutrients, good support matrix, and enhanced permeability.

Characterization of the Bacterial and Sulphate Reducing Community in the Alkaline and Constantly Cold Water of the Closed Kotalahti Mine

“…However, 15 years after the introduction of carbon substrates and SRB inoculum (e.g., manure sludge) the activity was seen to decrease followed by a decrease in pH in the deeper water layers in Vehkankuilu as well as increase in the concentration of sulphate and heavy metals in the water. The mine has been able to sustain the sulphate reduction activity for a relatively long time after inoculation, which is in accordance with the results obtained also e.g., in the Lilly/Orphan Boy Mine in situ bioreactor [55]. The majority of the bacterial communities in the flooded shafts of Kotalahti mine 15 years post inoculation belonged to non-SRB taxa.…”

Metal removal efficiency and ecotoxicological assessment of field‐scale passive treatment biochemical reactors

“…Anaerobic biochemical reactors (BCRs), also called sulfatereducing bioreactors, have been shown to be effective at significantly reducing or removing a variety of metals from mining-impacted water (MIW) [see, e.g., [1][2][3][4][5][6]]. Biochemical reactors are similar to constructed anaerobic wetlands; however, the MIW does not contact plant roots, such as is desired in a constructed anaerobic wetland.…”