Passive water treatment technologies are increasingly being considered for mine site
closure in the Yukon. Efforts are currently underway in Yukon to test, compare and
contrast passive treatment technologies with conventional technologies. This study
aimed to provide additional information about the effectiveness of passive treatment
technologies for mine water treatment in cold climates. To test the hypothesis that
bioreactors can effectively treat mine-impacted water at low temperatures, four benchscale,
continuous flow bioreactors were assessed for their potential to remove As, Se
and Sb from mine effluent over a one year period. More specifically, the objectives of
this study were to: 1) assess the efficiency of removal of As, Sb and Se from a synthetic
drainage with relatively high initial concentrations of the three metals in cold conditions,
as well as from actual leachate collected at the Eagle Gold site, a proposed gold mine in
central Yukon, 2) evaluate the effect of using wood chips as part of the composition of
the bioreactor, and 3) assess the effect of the freeze/thaw transition on the bioreactors’
performance.
Results show that all bioreactors significantly decreased As, Sb and Se concentrations
when carbon was added independent of influent concentration. Using the highly
concentrated synthetic metals drainage with an average of 4.9 mg/L As, 0.14 mg/L Sb
and 0.47 mg/L Se with a 1% methanol addition, the removal efficiencies were >93% ,
>96%, and >99% for As, Sb, and Se, respectively over phases 1 to 3.